I got the idea years ago after looking at MB Unimogs at a gov't sealed bid sale. Got talked out of the Unimog by a BLM employee when he told me they sometimes sit for weeks waiting for some obscure part. At the time I was using a W100 for plowing snow and thought it would be nice to sit further forward and higher for better visibility. Plus, I could get a crew cab on a much shorter wheelbase.
On a 1st gen CTD regular cab chassis you could have a crew cab and 8' bed or a serious mega cab and somewhat shorter bed. It would be strange looking but utilitarian.
The cab wouldn't be too hard to make using a swing open side door van and cutting where you want behind one of the side doors, sectioning out what you don't need and welding the rear "cap" on.
The things I haven't figured out are the steering and if there's enough room between the seats for the CTD. Also, the front van fenderwell could be an issue.
Is this a crazy idea?

 

In a word - yes. ;-)

 

What? no imagination?

 

It could work. Heck, you can get a Dud van for dirt cheap, not much risk, not cutting a Hemi Cuda in half.......I have many vans in the back yard here in NE. I have seen many ferd 4x4 van/ambulances and they get whacked into flatbeds in back. Look okay if done nice.

I don't see the regular pu bed fitting in, but a flatbed looks better. I have a van/camper duallie that was gutted and stripped for a flatbed hauler and not finished. Cool in its own way.

 

The idea of using a Dodge van for the cab occurred to me after seeing a class C motor home. It's basically a cab-over-engine set up in some ways like a Unimog. you can find the 1980s vans for cheap like you said. Still not sure about the steering, also shift linkage for an auto trans.. In some ways a manual may be easier. Using a w250 or 350 chassis would prolly be easier than swapping engine and drivetrain into the van chassis since the frame on the van is welded to the body.
I agree about using a flat bed instead of a pickup bed. Could even have a removable utility box for hauling the tools of the trade.
This was a "mental" exercise a long time ago that I had forgotten about until recently. I posted the idea to get some input.
Thanks