Did all 1989 Irocs come with 9-bolts? If it makes a difference, it is a 350 TPI.
Paul

 

in 89 i think only 9 bolt was offered in the iroc, but i'm not 100% sure.

 

All 89's camaro or firebird with a 350 were 9 bolts. However, not all 89's (or other model years) got them. For example: Both myself and a friend of mine had 89 iroc's (both 350 cars) which were 2.77 posi 9 bolts. My 89 that had a 305 TBI had a 2.73 open 10 bolt. Yes it was an actual iroc, but it was more of an appearance package with an RS drivetrain. I know all 86-89 g92 iroc's got 9 bolts with 3.45 on the 305 TPI/5 speed cars and 3.27 on the 350 autos. Non g92 5 speed cars got 3.08's. I know some were 9 bolts, however some could have been 10 bolts. Both were used in many applications (some disc, some drum). All non g92 iroc's with the 350 had the 2.77 9 bolt. I know another guy around here who has a 90 iroc g92 car with the 350/auto and his is a 3.23 10 bolt. I do know some 85 g92 TA's got 9 bolts, but I've never seen any evidence to show any 85 camaro to have one. Many camaro's and firebirds had them from 86-89. Some TPI firebirds supposedly had 9 bolts in the 90 model year, but how true that is I don't know. I've never seen or heard of any 90 camaro's that came with a 9 bolt. All 91 and 92 f-bodies had 10 bolts.

 

I have a 9 bolt in my 90 formula with G92 3.27s.