I actually have one of these vans, right now it is my work/play vehicle, but I have plans of expo'ing it out one of these days. There are some misconceptions thrown around here so far.
1. To get a good working 4wd van is not going to be cheap as they are getting pretty rare.
2. Don't know about the autos, but the 5spd transmissions are pretty tough and come with a 2 spd transfercase. The 4wd automatics (at least in the U.S.) only came with a push button 4hi. However, the 2spd case from a 5spd can be made to fit an auto.
3. They actually get pretty good gas mileage. I am a tile contractor and my van is my main work vehicle, it is always loaded with tools, saws, supplies, tile, etc...., most of my driving in it is "in town" type driving, and I consistently get 21 mpg. If I get a job that's farther out and do more highway driving, I easily get 24-25mpg. When I bought the van and drove it home to CA, one tank of gas I got 27mpg.
4. They have a 1700 # payload which isn't bad. They aren't fast by any means but the little 2.2L 4YEC is a good little motor. The biggest problem they have is keeping them running cool due to the radiator placement. Therefore, you really have to stay on top of your whole cooling system to make sure it stays cool. When I go to expo mine, I will be adding another cooler with its own fan either up front somewhere, or whereever it will fit.
Like was already pointed out, they are easy to steal just like the toyota trucks of the same time period. I will be installing a kill switch in mine real soon and definately would before anytype of expedition trip.
The motor can be a royal pain to work on sometimes, if you need to do much more than change/check fluids. Good thing is, if you were to use it to travel to mexico and farther south, parts are in abundance down there. Parts are slightly harder to find here and most guys I know who are really into their van, have 1 or 2 parts vans.
I try not to think about head on collisions when I'm driving mine.

Still doesn't keep me from having a perma-grin when I'm driving it though! I've had mine on some decent 4wd trails, and due to their weight distribution they climb hills like a goat. I've also had mine out in the dunes quite a few times. Aired down to 12psi, and had no problems. Some of you at last year's SnT probably saw me driving out during the poker run.
Mine has 213,000+miles on it right now and it's still trucking. It leaks some oil, but still pulls really well doing daily duty as a work vehicle. It is very common to see these go 300,000+ Mine's an '89 and I bought it last year with 205,000+ On the drive home, the temp needle started to rise a little while on I15 while it was close to 100* out. Was able to keep the temp at a respectable level with the heater running and made it home just fine. Even drove it through part of the Mojave Trail that way, just to get off the freeway for a bit. Anyways, I was already planning on going over the whole cooling system anyways, as I knew one of the problems was the fan clutch. Got home took the WP off and it was the original waterpump TEQ stamp on it and everything! You can guarantee, that I bucked up the cash to put another toyota waterpump on there, considering the original lasted that long.
Well now I'm just rambling, here is a link to my van with more facts.
UltimateYota.com - 89 Toyota Van Deluxe 4wd 5spd
Soda Lake Bed, on the Mojave Trail