Have an owner of a 1966 GT350 and he wants to install a 4:11 rear in the car. Does anyone make just a center section for this car? Anyone use a spool type differential? Looking for options to offer him
Assuming he has original chuck I would remove and just get a period correct 9" single rib case and install aftermarket equalok in it. They are pretty good just get through reputable vendor like quick performance. He must have automatic as he wouldn't notice much if 4 speed going from 3.89 to 4.11
In my 1969 SCJ, I had two pumpkins. Original N 3.91's, and also a 3.25 I kept in the car most of the time. Donor Pumpkin came from a Lincoln.
I also would leave the original intact, bag it and store it.
Tons of 9" housings out there, make sure correct axle splines, build what you want. A "N" of stronger is not needed for that car.
He won't be happy with a spool on the street. Detroit locker would be my choice just because I'm stuck in the 60s. A Trutrac is a good alternative. And yes any 9" junkyard housing will not break in this application.
https://www.eaton.com/us/en-us/skuPage.912A587.html