Cool van! I did a very similar thing for similar reasons. I needed something to haul a motorcycle but also get off road and camp. I'm still picking what I want to do inside but the suspension is done.
About gearing, I had a very positive experience with Unitrax in Anaheim. I installed a 3.73 with a full Eaton Detroit Locker and I think it came out to around $1100 for the work and they were done in just a couple days. I highly recommend the locker and would also recommend a winch for insurance.
Here's mine early on when we drove up Main Divide Road from Silverado
I've looked at them a half dozen times and considered purchasing one, but, I just look at the upper unsupported area at the right side of the tire and thing...man that's gotta move/vibrate like crazy on any semi-rough surface. Some type of reinforced stand off latch mount on the door itself (with some backside load spread plate) could really help that out... I like the idea of picking up the existing door hinge structure though..I have one and am underwhelmed. It bounces and rattles over bumps and their latch is definitely not built with off road use in mind. I'm looking into reinforcing it out of fear it will fail.