Crewcab 4x4 help

[bammax]

What would have to be done to turn an 80's crewcab dually into a short bed 4x4? I know there's info out there on the long bed to short bed conversion, but not much in the way of the 4x4 conversion. Were there any crewcabs produced that were 4x4 from the factory that I could try to track down as a starting point? I had originally intended on finding a Suburban 2500 4x4, but those are pretty rare in the below $3k price bracket. At least up this way. I figure a crewcab dually is easier to find and I can sell what parts I don't need to purchase what I do need.

Here's the final goal:
Seating for at least 3 adults
Enclosed area for carrying groceries in bad weather
4wd to prevent getting stuck in bad weather
Enough cargo space to carry around engines or fenders or such
Ability to tow about 6,500 pounds