[monzaz]

Gearheads78 is correct

You 8.5 will do the job on the street and at the track and it is what the car came with. 10 bolt 8.5 rears are still used today under 1/2 ton trucks. Do you think GM would keep a rear around for 3 decades if it was a bad design or weak? 8.5 was created as the best of everything out there in the muscle car days. all the 1970 -1996 cars were optioned with this rear.

I build the 8.5 10 bolt 71 72 rear for the buick guys all the time. 455 buick motors pound them and they hold the drag only cars we put 30 spline custom axles in and 30 spline eaton unit and they love them. They are also c-clip eliminated rears because the axle bolt in unlike a chevy 10 or 12 bolt.

10 bolt 8.5 rear use all the same pinion bearings and have the same pinion shaft size as a 12 bolt. carrier bearings are standard 10 bolt and the ringf gear is only slightly smaller in over all diameter...but in drag race application it does not mean anything ...larger ring gear diameter was designed to hold down heat like in circle track and heavy truck application. 12 bolt vs 10 bolt

the 12 bolt have smaller 3/8 bolts compared to 2 less larger 7/16 bolts...EVEN ford 9" rear is a 10 bolt rear it only has 10 bolts holding the ring gear in place.

Think twice before ditching the 8.5. If I were closer i would buy it from you to have as a core. 1200.00 is a little steep if you are supplying the housing but is the shop doin the work in the car or the rear out of the car?

carrier brakes remember that 8.5 have a different carrier break that most GM diffs.

2.41 2.56 is considered 2 series
2.73 2.93 3.08 3.23 3.42 3.73 3.90 4.10 and on are all 3 series gear sets.

call if you want prices on parts
Eaton type posi 389.00
gear from 139.00
rebuild kit 89.00 (does not include bolt in axle bearings) 65.00 extra for the axle bearings and seals

that is 617.00 in parts alone. If you think you or some one can do the install for 300.00 they you have just saved 300.00 . Jim