Yes it will swap right on. As Dino mentioned, the hump most likely will have to be changed. No big deal. Cut out the spot welded one from the 2wd, and put the 4wd one in place, mark the holes, drill them, and use nuts underneath. You can then spot weld the nuts on place, to make removal easier.
Got this e mail the other day. I'll leave out the name....
>>>Your page on body parts really helped. I switch a 87 2x2 and put it on a 79 4x4 running gear. It worked perfect , even the wiring harness plugged in to a perfect fit . THANKS for the help!!!! <<<
Not so hard to do. :>)
~Chuck
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Chuck's Chevy Truck Pages - Snowplowing Central
http://members.aol.com/csmith669/plowcentral.html