Re: radius arm suspension?
My guess is the van is way heavier, s.t. it's not a great idea. Once you get everything customized for the increased weight, you might as well have done something from a 1 ton. But hey, be pioneering, I'm not that familiar with radius arms to say it's a bad idea.
Thundersgarage.com has a lot of decent info, and there are some other random pages out there about 4x4 donor/swaps on vans.