Nice idea. I have seen this done with a car trailer and a very wrecked (in the rear) K3500... basically did the same thing. Cut the frame off behind the cab. removed the rear drive shaft (It was a bolt on yoke If I remember right) and pulled the 4WD level. They welded the trailer on to the stubs of the frame that was left.
It was a decent truck. Till the DOT got ahold of it
This van/truck I am sure has been DOT certified. The car hauler.. Not so much.
http://dallassmithcorp.com/axleless/cab-chassis/the-boss-van/
I can see from the photos this truck does have a transfer case. The tail shaft has been deleted so it most defiantly started out life as a 4 wheel drive truck. I am sure the push buttons are gone, and the unlocking hubs have been replaced with solid ones. However, one has to wonder. Was a Ford transfer case designed to take the full load of the engine and transfer it to the front of the truck?
Only time will tell on that one.