I used the later rear end on an earlier truck so the frame was already a coil spring frame. Since the 4wd frame is narrower (actually it is straight instead of flared out like the 2wd) you would have to make some kind of adapter plate for the top of the spring or air bag. There are some threads that show this, maybe a search of the site might come up with them. Also an article about the conversion
http://www.trucktrend.com/how-to/cha...wd-conversion/
Rg