Its probably not that bad, though I haven't looked at a 2wd one.
1.) new tailcone/possibly output for the 2wd tranny. Might be easier just to find a used 4x4 one at a salvage yard and see if they'll take the 2wd one as a trade in.
2.) Transfer case. Getting a JK one would probably be the easiest, but I'd honestly just do a 3.0:1 atlas.
3.) Front axle. Get the rubi one with the locker. regear as needed.
I'd think the steering and front brakes should swap over.
Oh, and DO IT.. you'd be doing a service to the Jeep community. 2WD Wranglers SHOULD NEVER EXIST