I replaced the 242 in my 90. It's an easy conversion, but you will no longer have the auto 4wd position. Another drawback is the dash lights won't work. They're direct bolt in if you get one with the same input (23 spline) from a Cherokee. I don't know if a 231 out of a Grand would be direct as I'm not real familiar with them. You would also need to replace the 242 shift gate under the t-case handle, which is easy as well. Just pull the plastic indicator off, pull the cotter pin out of the bottom of the handle and it's then just 2 bolts to swap the gates. If you don't swap the gates you can easily go into neutral on the t-case instead of 4wd high. When I replaced mine I also replaced the plastic indicator with one from a 231.

 

Awesome man thanks for the info! The shift gate is that the piece that's actually inside the jeep or the linkage underneath