I have a 72 skylark with a 10 bolt. I have a chance to get a 12 bolt from a 70 GTO. The sizing seems right, but i was wondering if anyone knew if I would have to cut the driveshaft down. Isn't the yoke about a half further forward on 12 bolt?? Any feedback appreciated.
You'd need 7/8-1" longer driveshaft to substitute the 12 bolt. Why the 12 bolt swap? For peace of mind, I pulled the the original 3.55 posi coded 12 bolt rear out of my '71 455HO GT-37, put it away, & now & in its place sits a disquised HD 8.5 A-body rear built with 30 spline Mosers, HD Eaton carrier, & US Gear 3.42's. Much stronger & safer rear than the McKinnion 12bolt. On that partricular HD 8.5 A-body rear, I assembled it w/ an original 3R 12 bolt pinion flange, & then needed a 1/2" shorter driveshaft. With an oem 8.5 3R flange would have needed a 7/8-1" shorter driveshaft. Got Posi? :3gears: Roger
