My early '69 GT350 (#100) has 5RS68 stamped on the leaf springs, and no other stampings. Does anyone know what colors would have been stamped on my build sheet for the leaf spring section? I can't find my build sheet.
My car has a few other anomalies as well.
The "build sheet" springs were removed by Shelby and replaced.
The replacement springs did not have colored stripes. They might have had a white marking on the front eye, but thats all
Interesting. Thanks.
The vast majority were special leaf springs that had the bottom and two upper a different length compared to regular Mustang . The typical 69/70 Shelby bottom leaf was marked S9MS 5560 A. There are two other different markings that I am aware of also. Yes as Pete mentioned they were marked with a sprayed on white marking encompassing the spring eye.
Were these installed on the Ford assembly line? Or were they swapped when the cars were completed by AO Smith?
(https://www.thecoralsnake.com/69springs.jpg)
AOSmith
What was the purpose of the spring swap? Can't imagine there was much difference in handling since nothing was done to the front spring if I recall.
69 shelbys were designed to have the new wide low profile f-60-15 polyglas gt tires and early shelbys had tractions bars so i think the new leafs were designed for better traction with new wide tires. 69 shelby leafs only used 2 round hole (not square hole) spring wraps not 3 like other year springs and bottom leaf lays flat and dont use a sring wrap. The front eyelet had white paint sprayed on the front end and the later cars started using c9zx bottom leafs along with the s9ms and i never could figure out why #s change as gt 350 vs gt500 vs 4-speed vs auto as nobody that i know of has figured out a pattern but the very early cars had 5rs68
Quote from: 98SVT - was 06GT on June 16, 2026, 11:30:38 AMWere these installed on the Ford assembly line? Or were they swapped when the cars were completed by AO Smith?
The build sheets show a conventional Mustang spring was used when building the car at the Ford assemblyline. The Mustang springs were swapped out at AO Smith during conversion.
Quote from: Bob Gaines on June 16, 2026, 03:55:57 PMThe build sheets show a conventional Mustang spring was used when building the car at the Ford assemblyline. The Mustang springs were swapped out at AO Smith during conversion.
So despite all the bad mouthing of the Shelby American line being too inefficient and all Ford's efforts to speed up production their own Shelby Automotive wasted time and dollars by not installing them during the initial assembly.
Thats an odd statement, considering Ford did not install "Shelby" unique parts any other time....
Quote from: Coralsnake on June 16, 2026, 07:13:03 PMThats an odd statement, considering Ford did not install "Shelby" unique parts any other time....
To reduce costs, Ford began installing more of Shelby's unique components directly at the San Jose assembly line before the cars were shipped to LA for final finishing. For example, the 428 big-block engines for the GT500 and the special exhaust systems were built-in. However, the remaining interior, fiberglass, and specific trim components were still finished by hand at the Shelby Facility.
To reduce costs, Ford began installing more of Shelby's unique components directly at the San Jose assembly line before the cars were shipped to LA for final finishing. For example, the 428 big-block engines for the GT500 and the special exhaust systems were built-in. However, the remaining interior, fiberglass, and specific trim components were still finished by hand at the Shelby Facility.
[/quote]
This is a different process used in 1967 versus 1969 when Shelby Automotive contracted with AO Smith to do the mods.
See attached pictures of what I have on June 69 build
Pete
Sure Ford installed some parts, but my point is that wasnt really part of the overall plan.
Would be interesting to see a side by side comparison of the Mach 1 spring that the car left the factory with and the spring A.O. Smith put in as far as length of the individual leaves. We know the top is the same and the bottom is different but what about the other two and did it retain the 550# rating.
Also, was ford making their own springs back then or using an outside vendor? If made in-house, did they also supply the Shelby spring to A.O. Smith or did Smith use their own vendor. Is it JRS spring that is also located in Michigan? More questions than answers.
Quote from: Dennis Y on August 10, 2026, 07:42:36 PMWould be interesting to see a side by side comparison of the Mach 1 spring that the car left the factory with and the spring A.O. Smith put in.
Also, was ford making their own springs back then or using an outside vendor? ............
Ford used multiple sub contracting companies to supply leaf springs for the many different needs and al those plants around the country.
AO Smith would not have chosen the springs. That was Ford.
Ford built the car with their springs and AO Smith replaced them with the Shelby specified springs.
I have been told the springs were made by Rockwell, but I have not confirmed this yet. The small keystone stamp on them maybe a clue.
Quote from: Bob Gaines on June 16, 2026, 11:27:13 AMThe vast majority were special leaf springs that had the bottom and two upper a different length compared to regular Mustang . The typical 69/70 Shelby bottom leaf was marked S9MS 5560 A. There are two other different markings that I am aware of also. Yes as Pete mentioned they were marked with a sprayed on white marking encompassing the spring eye.
Ed will clear this up but IIRC some were marked C9?
Quote from: TLea on August 11, 2026, 11:24:16 AMQuote from: Bob Gaines on June 16, 2026, 11:27:13 AMThe vast majority were special leaf springs that had the bottom and two upper a different length compared to regular Mustang . The typical 69/70 Shelby bottom leaf was marked S9MS 5560 A. There are two other different markings that I am aware of also. Yes as Pete mentioned they were marked with a sprayed on white marking encompassing the spring eye.
Ed will clear this up but IIRC some were marked C9?
S9MS,5RS68 and C9ZX are the ones I am aware of.
Mr Gaines are the C9ZX Shelby unique?
Does anyone have pictures of these?
The c9zx show up late but look the same as s9ms. I once thought auto vs 4-speed staggered shocks were the change ID #. but thats not the case either or big suspension change but i ruled that out also. So i think its more of a ford # changeover just like 69 b9 parts started off kkx then went to c9zx same part just a running change.
Quote from: Dennis Y on August 10, 2026, 07:42:36 PMWould be interesting to see a side by side comparison of the Mach 1 spring that the car left the factory with and the spring A.O. Smith put in as far as length of the individual leaves. We know the top is the same ang the bottom is different but what about the other two and did it retain the 550# rating.
The two inner leaf's are longer on the 69/70 Shelby at 46" on the upper and 32 1/2 on the lower compared to a regular Mustang regardless of year (65-70) or application. I don't have the measurements on the earliest 5RS68 marked Shelby leaf spring.
My May 6 built at Dearborn plant car springs.not sure on the conversion day at Smith. I just pulled this down from my attic as a local guy is going to reproduce them and needs one of mine for dimensions.,
69 Shelby spring on the left and 1968 GT500 FB spring on the right. Not sure if a 69 would have diff spring lengths than a 68
69 shelby 2 round hole wraps vs mustang 3 square hole wraps
Quote from: shelbymann1970 on August 11, 2026, 06:18:51 PM69 Shelby spring on the left and 1968 GT500 FB spring on the right. Not sure if a 69 would have diff spring lengths than a 68
Yes the length of some of the leaves are as well as the hardware as Ed mentioned
Quote from: Special Ed on June 16, 2026, 02:19:16 PM69 shelbys were designed to have the new wide low profile f-60-15 polyglas gt tires and early shelbys had tractions bars so i think the new leafs were designed for better traction with new wide tires. 69 shelby leafs only used 2 round hole (not square hole) spring wraps not 3 like other year springs and bottom leaf lays flat and dont use a sring wrap. The front eyelet had white paint sprayed on the front end and the later cars started using c9zx bottom leafs along with the s9ms and i never could figure out why #s change as gt 350 vs gt500 vs 4-speed vs auto as nobody that i know of has figured out a pattern but the very early cars had 5rs68
Not sure how much this helps but page 35 calls out a 69 GT350/500 spring with less free arch springresearch.org/pdf/volume_17.pdf
I think its a great contribution.
So here is what I found:
The part number for one of the Shelby springs is C9ZZ-5560-J
Am I reading this correctly?
It was marked C9ZA-5556-S if used on a Boss 302 and S9MS-5556-A if used on the Shelbys.
Its possible that Shelby didnt want to use "boss" parts, so even though the spring is the same they just rebranded it. What do you think?
https://www.boss302.com/spring.php
Now we need to find the other two versions
Does anyone have a picture of the later C9ZX spring??
Has anyone noticed a change in the bushings on these Shelby springs?
Quote from: Coralsnake on August 12, 2026, 09:21:07 AMI think its a great contribution.
So here is what I found:
The part number for one of the Shelby springs is C9ZZ-5560-J
Am I reading this correctly?
It was marked C9ZA-5556-S if used on a Boss 302 and S9MS-5556-A if used on the Shelbys.
Its possible that Shelby didnt want to use "boss" parts, so even though the spring is the same they just rebranded it. What do you think?
https://www.boss302.com/spring.php
Now we need to find the other two versions
I don't believe the MPC shows what was assemblyline. I believe what you are reading in the Master Parts Catalog is a case of as it has to do with a service replacement part vs assemblyline part. The Boss leaf springs are the closest thing to substitute as a service part to the Shelby leaf set is my guess and was used to service both if needed. The Boss 302 spring when compared side by side to the S9MS leaf has the two inner leaf's shorter not to mention the curved bottom leaf compared to S9MS marked leaf set with its 2 longer inner leaf's and its straight bottom leaf. Although I have several sets of S9MS leaf sets here in my shop now unfortunately for this thread sold all of the the C9ZA-S leaf sets I have had over the years that i could have used to show a side by comparison. The side by side difference is somewhat dramatic.
Mr Gaines, thank you
So are you saying the C9ZA-5556-S and the S9MS-5556-A are not the same spring?
(https://www.saac.com/forum/gallery/8-120826111439.jpeg)
Im not saying you're incorrect, but it would appear they are the same as both IDs are included together
Quote from: Coralsnake on August 12, 2026, 11:16:28 AMMr Gaines, thank you
So are you saying the C9ZA-5556-S and the S9MS-5556-A are not the same spring?
(https://www.saac.com/forum/gallery/8-120826111439.jpeg)
Im not saying you're incorrect, but it would appear they are the same as both IDs are included together
As I have already said It would appear to be a case of a service replacement part vs assemblyline part given the physical differences between the two.
Ok well, I will work on a new theory
I am full of them 😆
There was similar information on those springs on a chart from General Spring in iirc Kansa City MO. I'll have to go back and look for it.
In reference to reply #30, another question, were the 69 Boss 302s in production yet when Shelby ordered the Mach 1s used to start building the Shelbys? Maybe B2 springs were not in production yet, but specs were known. Since both cars have a similar squat, it would seem that it could be the same spring.
Im going to say I strongly feel like the company was Rockwell Standard
(https://www.saac.com/forum/gallery/8-120826144009.jpeg)
Heres a picture of a z28 Camaro stamping. Rockwell did springs for GM and Ford
Mr Gaines is saying the the Boss springs are visually different and I believe him
Can't find the chart I was looking for on the General Spring site but their listings do show the same industry #42-503 for the GT350/500 as the Spring Research chart. General is not showing a listing for the Boss 302.
Quote from: Dennis Y on August 12, 2026, 03:07:59 PMCan't find the chart I was looking for on the General Spring site but their listings do show the same industry #42-503 for the GT350/500 as the Spring Research chart. General is not showing a listing for the Boss 302.
I suggest you re read my post #24 and do the homework if you want to know the real answer.
I agree all this extra stuff is noise. It doesnt matter what other companies like Eaton, springy thingys and General are offering as replacements. ( if they even are ) We are concerned with the OEM assembly line springs.
We were working on the s9ms springs back when chris brown passed RIP ole buddy and chris had a machine shop making the unique lower flat leaf and stampping the #s since the rest of the spring can be found from other springs. I sent an odd s9ms lower leaf i had here to chris but not sure if i got it back but if someone wants to finish making the spring i can loan my s9ms leaf out.
Just to support the discussion and add some addition information and documentation. These are from Ford and what they used to assemble the cars provided to AO Smith
Checked what is commonly referred to as the add/delete sheets and on the copies/forms I've got it shows
One set of sheets shows
Items to be selected #9393368
Items to Omitted Rear Springs (2 Stage)
Description REl. 1-22-69 -Per Trans. X9A-291
++++++++++++++++++++
Then looking at a later sheet dated 1-22-69 it shows. Likely the form referenced above.
Items to Omitted Sportroof - C9ZA-5556-C or G(difficult to make out) Rate 135-141 & Load 670-710
Convertibe - C9ZX-5556-A Rate 128-142 & Load 715-775
Items to be selected/installed Sportroof - C9ZX-5556-A Rate: 128-142 & Load 715-775
Convertibe - C9ZA-556-E Rate 135-141 & 710-750
It is interesting and a puzzle since the buildsheets used on the line to construct the cars at Ford still listed the standard (for the application as a Mustang) rear spring markings.
Hope this helps
Quote from: Dennis Y on August 12, 2026, 03:07:59 PMCan't find the chart I was looking for on the General Spring site but their listings do show the same industry #42-503 for the GT350/500 as the Spring Research chart. General is not showing a listing for the Boss 302.
Might have to do with the fact that the Boss 302 was only produced during the later part of the production year- sometimes referred to as a 69 1/2 so depending on when the data was collected and published that might explain it. Same thing happened with paint codes as late and mid year paint chip pages didn't include those Boss 302 exterior only colors on the sheets.
Quote from: Coralsnake on August 12, 2026, 02:43:53 PMMr Gaines is saying the the Boss springs are visually different and I believe him
Can confirm that also with my low mileage very early built 69 Boss and others I've seen.
Mine are marked (lower) short leaf - C9ZA-5556-S Dated 20 days before the car was built.
Ed there is a guy working on this now
I can send you his contact
Does anyone know how the C9ZX springs were marked?
Bob --- sorry, maybe I mis-phrased my question as I did not know if anyone had the measurements for the Boss 302 springs and was just musing which springs were made first.
Jeff --- what is the early build date of your Boss
Ed --- looks like Shelbymann1970 also has a SMS lower leaf that he is using with his person to reproduce.
Gary -- keep us up to date with your endeavor. I"m sure a lot of us would be interested.
To all --- thanks to everyone for their input. I have seen this topic come up a few times over the years and just seems to loose steam for whatever reason. Hopefully this time a solution can be found.
I know I lack a lot of the knowledge of most on here but just trying to participate and help find answers
Thank you all!.
Quote from: Dennis Y on August 12, 2026, 08:12:24 PMBob --- sorry, maybe I mis-phrased my question as I did not know if anyone had the measurements for the Boss 302 springs and was just musing which springs were made first.
Page 25 of this Spring Research version has the 1970 B302 measurements. https://springresearch.org/pdf/volume_18.pdf
These were written specifically for aftermarket manufactures to build to OEM (or very close) specs. Note that the B302 spring is assigned the same 42-503 number as the GT 350/500 replacement however the free arch of the the OEM is 1/4" different.
I have no doubt the OEM springs are visually different as pointed out already.
Quote from: Special Ed on August 12, 2026, 04:59:49 PMWe were working on the s9ms springs back when chris brown passed RIP ole buddy and chris had a machine shop making the unique lower flat leaf and stampping the #s since the rest of the spring can be found from other springs. I sent an odd s9ms lower leaf i had here to chris but not sure if i got it back but if someone wants to finish making the spring i can loan my s9ms leaf out.
got a local guy who wants to see my spring to make some up. The guy who is the " middle man" owns a 70 drag pack car he bought early 70s and bought new springs (D0) and all the cables and battery tray for boss 9 to put a trunk mounted battery into his 70 when he worked the parts counter at a ford dealership. Realized decades later the D0 springs he out on are not correct so his friend is embarking on making some springs. This Shelby owner when he worked at GM gave Max thousands of fastener blueprints so AMK could do GM fasteners.
My car 48-1014 produced 21 of february has the S9SMS-556A springs
Tor
I'd like to get my 5RS68 springs re-arched if anyone is is still doing it. It probably won't be permanent but it should help reduce sagging for a few years.
Quote from: 69 GT350 Vert on August 13, 2026, 07:21:42 AMI'd like to get my 5RS68 springs re-arched if anyone is is still doing it. It probably won't be permanent but it should help reduce sagging for a few years.
We have several places in KC that do re aching of leaf springs. I would double check in your area with the truck repair community for spring re-arching. I get the impression it is still a widely available service.
I'm lucky as I have Eaton Springs " in my backyard".
Hey 69 GT350 Vert, what number is your car? I am trying to figure out which ones should be on my car. I bought it back in 86 while I was still living at home and tore it apart in 88 before cell phone cameras (I think) and had no idea that they were different than a stock Mustang spring. For a number of years after that some of the parts of the car were there and some were here until I got my garage built here. I don't know what happened to them as I was also running a small block Maverick back then and don't know if my dad figured they were scrap or what but unfortunately he was not a big fan of my car addiction. Anyway, just trying to figure out which ones I should have if anyone is sucessfull in getting an accurate copy made. Thanks, Dennis
#100. I'm not sure if the 5RS68 leaf springs is an early/late thing.
Quote from: 69 GT350 Vert on September 01, 2026, 09:37:55 PM#100. I'm not sure if the 5RS68 leaf springs is an early/late thing.
Yes, the 5RS68 leaf springs are typically an early production thing.
Quote from: Dennis Y on September 01, 2026, 08:17:48 PMHey 69 GT350 Vert, what number is your car? I am trying to figure out which ones should be on my car. I bought it back in 86 while I was still living at home and tore it apart in 88 before cell phone cameras (I think) and had no idea that they were different than a stock Mustang spring. For a number of years after that some of the parts of the car were there and some were here until I got my garage built here. I don't know what happened to them as I was also running a small block Maverick back then and don't know if my dad figured they were scrap or what but unfortunately he was not a big fan of my car addiction. Anyway, just trying to figure out which ones I should have if anyone is sucessfull in getting an accurate copy made. Thanks, Dennis
The problem I see is that the S9MS Shelby leaf springs are unique and besides the bottom special leaf the next two leaves are different lengths compared to a regular Mustang or Boss leaf. I think I read where one of the members was trying to have just the bottom special leaf made which is better than nothing but still not correct.
Bob, do we have any info as to when (either by date or car#) the change from 5RS68 to S9MS occurred?
Hey 69 GT350 Vert, could you possibly get measurements of you middle 2 springs to see how they compare to the S9MS ones that Bob has measurements for to see if they are similar?
Anyone else out there with the 5RS68 springs, could you post your car # and build date if you have it to add to our info?
THANKS!
I don't have access to my car for a while. I'm not sure measuring springs installed on a car will be helpful. My springs have sagged a bit.
I can do some measurements when I get the car back.
Quote from: 69 GT350 Vert on September 04, 2026, 08:31:51 PMI don't have access to my car for a while. I'm not sure measuring springs installed on a car will be helpful. My springs have sagged a bit.
I can do some measurements when I get the car back.
The length of the springs should not be different sagging or not.