The conversion is not as easy as it seems it would be, to do it you will have to get the whole stamped steel rearend piece that the tailights bolt onto from a 90-91 and have it welded in place of the 89's. I don't remember if you need to swap trunks or not. Google it, and you will find it. I found a write up when I was looking into it for an '89 I had.

Welcome to HAN, BTW.