Its a 9 bolt disc.....just trying to figure out what year it was out of so I can figure out what calipers to get.

 

your leaving alot out, you said its a borg warner 9 bolt. are you switching to rear disc? are replacing pbr's ?

 

I have already switched my rear end...im curious to know what year iroc it came out of. Are all 9 bolt rear calipers interchangeable?

 

the early calipers were cast iron the 88-92 are aluminum they use different mounting brackets and rotors

 

Are you sure about the start year? I have a rear end out of a notchbach 1988 GTA with the 10.5" rotors and iron calipers

 

if yours are cast iron than still the j65 option maybe the start year of the pbr's were 89 I can't remember.

 

I'm guessing 89 was the full year with transition pbr's in late 88?

 

88 AFAIK got the Saggy brakes. No PBRs unil 89 except in the 4 (!) 1LE cars, and maybe the Players ones, I don't know much about those.

Bottom line is, if the calipers are aluminum and the rotors are 11.7", they're the 89-up PBRs; if the calipers are cast iron and use the same pads as the front and the rotors are 10.5" (same as the front) they're the 88-back Saginaw.