- Jan 2, 2006
It’s not an improvement per se. It’s certainly a good rear but a bit overkill if you’re just wanting to upgrade your stock rear to posi, IMO. A stock 8.5 will hold up to some abuse. Spending more money than you have to is optional. If you’re running a stock 307 or even a stock 455, the 8.5 will hold up without issue and last the life of the car, properly maintained. It’s already been 38 years. For a few hundred bucks and a little luck with your gear set condition, you can make it last another 38 years with a freshen up.