Have an 89 350 with crew cab. It needs some osfo soon and a new coat on top.
Thing is, I keep seeing single to crew swaps, none the other. I want a single cab to make more room for a flatbed. That gives me two foot maybe, 10' flatbed for a camper build. The frame drop down would make a nice step down on the bed to enter the back of the cab. Mental block was having to purchase a cab, but as many 2 to 4 swaps out there that doesn't seem to be a problem. An extended cab may be better but gets into the frame transition im aiming to be the step down on the camper floor/flatbed.
I know, lose the crew for a single? Crazy, but, I have a plan.. lol
The whole idea is to put a box back there. Soooo flipping big the ole lady wont drive it, and I can just move into it and split when necessary, being "she dont camp". So if anybody as some cab reducing tricks along with built on camper ideas I game for reading them.

 

That's an interesting idea, offhand I'd say custom rear cab mounts would be the biggest obstacle. Shouldn't be too hard as long as frame differences don't interfere with the bottom of the cab.
Take plenty of pictures for us if you do it!

 

you could just cut the back out of the crew cab and use the floor that exists as the step down maybe

 

Or sell/trade your crew cab for a straight truck. OBS crew cabs are getting rather rare.