I'm not sure how they're going about it, but I've seen some GM 8-lug vans with Quigly 4wd conversions that looked like they retained the IFS setup... Like they're using the 2500 truck front end on the van. makes it a little taller, but if you are after 4wd without needing extreme capablilty, that might be an option too. If you're looking for an older van though, it's not very helpful.
Good luck!!!