Don't quote me 100% on this but I believe the tailshaft on the transmission is different in 87 and 88 so you will need a 4x4 trans and case, not sure from 89 to 93. I do however have a 4x4 frame in pretty good shape, but I already tossed the motor and trans (sorry couldn't even give it away). The problem with the RX7 diff is most were IRS setup, while cool it's a lot of work for what you get, good handling but poor straight line traction. An alternative that is much easier is an 8.8 solid axle from a 94-04 mustang, 93-97 ranger 4.0, or 95-01 explorer, and most of the rangers and explorers came with a posi unit. The other problem you might run into is the 2.0 with four wheel drive will be way underpowered. Thats why I'm sticking a 351 windsor in mine.