I have an 85 z28 and I recently pulled another rear end out of a 1992 z28 standard. I'm new to messing with rear ends and I'm not really knowledgeable on the subject. I'd like to install a posi unit onto this donor rear end. Which cars can I take one off of that would mate with this one?

 

In 89 they switch to a higher spline count. Any 7.5 10-bolt (82-02 F-body hat isnt a 9-bolt) carrier will bolt inside your rear end. But the 82-88 axles are different form the 89-92 ones. 93-02 posi units will fit 89-92 axles.

Dont get any posi unit from an S10. Ever. They're not a terrible source to harvest gears, but the posi used in those isnt really a posi... it's a sort of craptastic locker that will explode on you unless you drive it on sand everywhere.

 

1990-up are 28 spline,posi carrier from 1990 up through 2002 will fit-I test fit a torsen posi from a '99 z28 into a '90 housing and it all fit using the '90 28 spline axles.Though I haven't done it yet,i plan to install this posi into my '82 housing using the'90 axles-(the '90 housing was damaged,later axles,~1990 up also have the pinion bearing area reinforced with revised ribbing VS earlier ones in order to reduce deflection of the pinion)

 

https://www.thirdgen.org/forums/tran...-10-bolts.html
It would be easier if you just read this. There is more to it than just the axle splines. You also have to get the correct series for the gears that you have.