Just thinking random thoughts. Was throwing this around in my brain. 4.0L in-line 6 - plenty of torque, ok Hp, plenty of mods available, prolly can be picked up cheap. What about swap footprint? Can’t be much different than 4.6 V8? What about adapting trans and transfer case from a wrangler TJ?

 

I think that most any engine/trans that will fit with basic changes like motor/trans mounts and drive shafts is pretty simple.
The problem is the wiring and gages.
If you want to retain the D2's abs and hdc you need to make the D2 electronics talk to the new drive train, that's where the work is. And, of course bell housing or transfer case adapters if you plan on reusing any of that.

The 4.0 six is longer than the 4.6 is too, so you have to consider how much room you have to work with.

 

With a big enough shoehorn, it will fit in. It has been like 20 years they do not built cars anymore; they make now computers with wheels. Your problem is electronics, not the mechanics of it.