Hard. You would need a transmission for the 3.0 which would require either an adapter or new transfer case to keep the 4 wheel drive working. Plus I have no idea if the lengths are all the same on all those units so mounts would probably need to be moved, etc. It's way more hassle then it's worth.
Just go junkyard hunting for a 4.0 OHV. It's a better engine then the 3.0 anyway (least IMO).