I was looking into an AWD or 4WD van for a while, but in the end they are too pricey for the utility. I wanted a family hauler, but GM made almost no vans with nice leather seating ("luxury package"?) and AWD. So you're looking at a conversion package, which even in the used market is like 50% more money. They are mostly "church bus" style just designed to pack in lots of seatbelts. Even keeping the IFS, you can swap the transfer case to get real 4WD. There is also a way to lift them using Avalanche knuckles or something and the axle shafts are still at a good angle (shafts angle down, where stock they angled up). But even without the extended roof it's not going to fit in a 7' garage door. And how often do you really need to stand up in a passenger vehicle?
Then you look at Tahoe/Suburban/Yukon which came stock with 4WD, Leather seating or even up to 9-passenger, for sale on every other street corner for 1/2-the money as a van. Plus it gets a few more MPG. If you were really going to use the van as a camper then it might be worth the premium $$, but otherwise not too practical of a choice.
EDIT: I wonder if there a diesel that would fit in there.