dwh
Tail-End Charlie
I don't think those ever came 4x4, so any conversion is going to be completely custom. The only guy I ever knew who did it was Mike "Dr. D." Duncan, the Four X Doctor:
http://www.fourxdoctor.com/
But he sold his decades ago. All I remember about it was that the front was on leaf springs and the front spring hangers were beefy custom welded boxes. You are going to end up having to make spring hangers.
If it were me, I'd start by getting the running gear out from under the front of a Dodge 4x truck of about the same year. Dodge wheels have bolt hole spacing that doesn't interchange with Ford or Chevy, so you need a Dodge front axle.
Most of the Dodge trucks from back then were full-time 4wd so you need to try to find an axle that either has manual locking hubs, or can be fitted with them.
Same with the NP203 transfer cases that most of them had - full time. There are conversion kits to make the 203 into part time, but if I were starting from scratch I'd go with a 205 instead of jacking around with the chain drive 203.
Your transmission will have a tailcone and output shaft that won't work for a transfer case, so you'll need both a tranny and transfer case. And a different trans crossmember. Get all of that from a donor vehicle.
Most vans have a crossmember under the engine which will end up directly above the differential, and get smacked when the suspension compresses, so you might have remove it and make a new one a few inches further forward. And then figure out how to keep the diff from bashing the oil pan up into the crank.
The steering on the 4x front axle won't work with the steering box in the van, so you'll end having to figure out a way to get the tie rods to line up and connect properly with the steering box - without having suspension movement cause the geometry to get out of whack when you hit a bump.
You'll need a front driveshaft, and it won't be the right length - but after you put in the transfer case the rear won't be either so you'll have to take them both to a shop to have them redone.
Basically, it's going to be a major PITA requiring some serious fabrication skills and a buttload of homework and planning. It can be done, and the parts aren't all that expensive, but be prepared for the truck to be sitting on jackstands for a few months.
