I agree with Billy. Swapping to an old jeep is downgrade for the entire drivetrain. I had a 90 YJ before I bought the VX and it was by far the worst vehicle I ever own. I put so much time into chasing oil leaks on the 4.2L AMC junk engine (112 hp) and eventually decided selling the Jeep was easier than stopping all of the leaks. I don't dislike Jeeps at all but just had a really bad experience with mine.

IMO, to make a jeep swap worth the time & money:
1.) 91'+ model year to get the 4.0 fuel injected engine
2.) Dana 44 rear axle or equiv., most wranglers have a Dana 35 which is a downgrade from the 12-bolt.

If I had severe drivetrain issues on the VX, I would consider an 03-06' Jeep Rubicon swap as a viable option:
4.0L engine
6 speed manual
4:1 t-case
dana 44s front & rear with lockers
coil springs
93.4" wheel base

The only problem is that all of the Rubicons, used or wreaked are $$$. You might find a regular jeep donor with aftermarket upgrades to make it worth the swap. Otherwise, you have to ask what you plan to gain from the drivetrain swap.