I think the factory AWD van uses some of the 1500 front end parts. Note that it's the light chassis (6 lug wheels) that they offer as AWD, not the heavier chassis, which has 8-lug wheels. Quigley does conversions on the heavy chassis, but not the light one. I'd pull up next to a few silverados and see what looks similar. You'll probably want to compare to the 2007-up 1500 trucks. You might find enough similarities that you could mostly bolt in the front AWD components, but I just don't know. If that doesn't look right, then see if the '06-down 1500 chassis matches up. ??
Your 4.8 would probably be ok with 4wd, but you're going to want to put a t-case in it with low range if you plan to spend a lot of time in the sand.
Good luck!
Chris