My 89 IROC's Australian 9 Bolt is making alot of noise once you exceed 30 miles an hour. My mechanic is trying to locate a 10 bolt posi from a 3rd gen car. I was just wondering if a 4th gen f-body rear would fit?

 

Yes it will. My buddy with an 89 with the 9bolt put one in. The only problem is that the 4th gen rear end is 2in longer on each side.

 

Thanks, that answers my question.

 

It'll fit, you just should use the 4th gen offset on the rear wheels after the swap.