Will this work? I found a 98 rear with 3:23 gears and the posi complete rear for 200. I think I read on here that someone did this but had to use different back spacing on the wheels. My car is a 89 RS with the regular rear for a auto with no posi.

Please before asking...Everything you asked is answered weekly...Because of people not using the SEARCH feature.

In other words yes. If you have anymore questions... Use the please.

Your 89 will probably still have 26 spline axles. The only strength increase with a 4th gen diff is the 28 splines axles.