With the 4.3 swap, you still plan to use a Jeep tranny, the AW4? Would the GM tranny be better? They have 4-spOD autos and bolt right behind the engine. The 4.3 was in many GM trucks as well as the 4-spOD auto with a driver's drop NP231 behind it. Though not a Jeep NP231, but a GM NP231 with slip yoke. There isn't much following for a SYE for them, but H&T should work. Or look at doubling or other options on the tcase?
You could look at adapting the Jeep tcase to the GM trans or Jeep trans/tcase to the GM engine.
How about a 3.9l Dodge V6 as an option? They are in the fullsize trucks as well as the Dakotas.