Like the title states, can I use a 8.5 truck posi and it's 3.73 gears in my 96 formula, assuming the splines all match? I found a good deal on one locally but just want to make sure. I'm not swapping the complete rears just the posi unit and gears. Will it work?

 

I doubt the larger carrier and gears will fit. Never have heard of anyone doing it (not to say it can't be done-it just does not seem likely).

 

Go to Thorobred or Brown and Brown and try to get them to show you the two different ones. Or see if they even might be the same thing.

 

no.

the stock rear is 7.5