Personally I swapped frames, I was very green when I did it, not much experience with wrenching, found a rolled Ranger with the same setup but 4x4, put my engine in it and swapped bodies, most of it was done in a weekend if I remember right from 2005...
To swap to stock 4x4 you have to swap engine crossmembers (welded and riveted in) which would be a pain since the engine is bolted to it... that and the passenger side frame rail is boxed on a 4x4 and not on a 4x2 and a few other details... Sure it's possible to skip some steps and throwing a Jeep Dana 30 solid axle saves some things but it's some work and not the easiest first project unless you swap frames... With like 4 people you can swap bodies on a Ranger, it only takes 2 for the bed but the cab is heavier, and don't forget the cable between the front seatbelts that goes around a crossmember...