If new, and if you're looking at Sportsmobile conversions, then the Sprinter. Six cylinder diesel.
If looking used for Sportsmobile conversions, also Sprinter. Not many full sized vans with 6 cylinder engines, and none by Ford since maybe the late 90s?
A smaller engine in a standard SMB (Sportsmobile) conversion would be pretty stressed, unless diesel, like the Sprinters. They do appear bigger, but in fact they have a good turning radius and aren't as ungainly as they may appear.
I get the impression you're looking for something smaller than a SMB. There are still lots of VWs out there, but they're getting harder to find and have some obvious disabilities. And don't even think about Eurovans. But check this page out; this dude is one sick van fan:
I think he wound up with a SMB, but boy did he find some cool vans (octopup?)
And I've been wondering about the backpacker eurotrash Burner rental specials I've been seeing lately, like Jucy and Wicked (if you're old here's what I'm talking 'bout: http://www.examiner.com/article/jucy-re ... s-by-storm
). Somebody is converting those vans, ususally mini vans, probably with FWD (front wheel drive) and V-6s, and maybe you can find out who does it. Some are rather nice, and I think one of them may even offer 4x4. If you find out, let us know. I haven't been able to.