im actually in the planning process of doing this on my mounty..
i have all the front end parts, transfer case, and driveshafts (rear and front) available to be be purchased..
all the front end components...(ie suspension control arms hubs etc ) are the same on a 2wd and 4wd..
the only pain is the output shaft of the tranny is shorter on the 4wd models..
basically meaning you need someone to take apart the transmission to swap the shaft (its the last part to come out the tranny) ...basically you need a 1000$ tranny rebuild just to swap the (4$) output shaft...
right now the output shaft is the only thing standing in my way..as soon as i can find someone to swap it for me for relatively cheap $400 or less ill be moving foreward with it
now if the tranny on your donor truck is good you could prob swap the trannys out and you should be set..
just make sure the engine model, tranny model and gear ratios in the diffs are the same..
im no tranny expert but id imagine having say a 3.55 in the rear and a 3.73 up front (or vice versa) could cause some problems
also on another note if i do this im not gonna be going through the cars computer..mine would be selected manually with a custom lever rigged up to select the 4x4 range and a 12v line swichted to the case to engage/disengage the electronic cluch
sounds complicated...well it is but after all my researching with the right parts its not too difficult of a task