Another slight "wrench in the works." What year is the Jeep, IE is it throttle body EFI or multiport EFI, or are you going back to carb or "something else?"
Dodge went to MPI in '92/3. All Chrysler engine Jeeps are MPI.
I don't recall how wide the ZJ rears are off-hand, the WJ and JK's are out in left field but many of the other Jeeps have rears only a bit wider than an A's. (and the same perch distance- but ZJs have a link setup in the rear) I noticed you didn't specify the year- apparently OBD-I 318 Jeeps had Dana 35s, OBD-II 318 Jeeps had Dana 44s- only the niners were guaranteed to have LSDs in them.
GT was just a trim on Darts and a lot of other cars back then. It had basically no relation to performance like mid '90s Mustangs caused people to associate with the badging- it's just the gilled-up fancy Dart, many had 6 cylinders. Transmissions you could use would be Dodge truck overdrives (some work making it fit), small block 727s, or small block 904 variants- no 4wd transmissions for a 2wd though and since this won't go in a Jeep you can't use a Jeep trans, only Dodge car or truck with a small block.
If the Jeep's full-time, the case's basically scrap- front axle's worth a bit though, people like to put them in 2wds and Rangers. Ditto on the Jeep trans- send it down the road, it's not of use to this project.