I am not that familar with ford's part numbering. I can't find the meaning of prefix S2MS. Any help would be appreciated! Thank you, Bill
There are several webpages and YouTube videos describing the part numbering system.
Ford used engineering part numbers and part numbers for the same part. The numbers on a specific part are often an engineering reference and not an actual part number.
The prefix was designed to provide information on the year and product line the part was originally designed for, since parts were often interchangeable and provided to other product lines, the prefix will only give you a rough estimate of that information.
An "S2MS" is a 1962 Shelby design. However the part may have other applications and usage. Most vintage 1960s parts will start with the letter "C" as that normally designates the decade for the 1960s parts. The "S2" part is obviously an exception to this rule.
Learning the base numbers is probably more helpful in identifying parts.
S2MS is not part of the Ford parts numbering scheme.
Shelby American was their own company but did model their parts numbering system after Fords.
S= Shelby
2 = 1966
M = I assume was for Mustang GT350
S = Special order part (is what it means on a Ford part)
I don't think the 2 refers to a 1962 part since S1MS was used on the 1965 GT350 and S2MS on the 66 ones.
If following the Ford numbering structure strictly the manifolds would all be S1MS and there would be a B change letter at the end to indicate a revision not a change to S2MS for the prefix.
This is good starting place for Ford parts - https://www.fordification.com/tech/partnumbers_overview.htm