I own an 88 iroc without posi and have access to a 3.73 posi out of a trans am/ firebird from unknown year but between 82-92 with disc brakes. Can the posi rear just bolt in. thanks, John from Detroit.

 

Sure does, takes an afternoon and you'll need to swap out or modify your proportioning valve since the disc brakes use a different bias. The parking brake cables are also different so you'll want the correct ones.

For the prop valve you can either get a disc valve, aftermarket adjustable valve or several people here, me included, have taken the spring and plunger out of the drum valve and sealed up the hole in the end plug with a machine screw and nut resulting in a 50/50 bias.

If you do a search there is a thread on the whole spring/plunger mod that includes detailed info and pictures with several reviews by people who have done it.