I like the idea of finding a small travel trailer to mount onto the truck's frame. It would save alot of camper building time/effort and simplify the whole buildup of the truck. I agree a small older Airstream, Avion or Silver Streak aluminum trailer would look really slick on that '59 truck cab/chassis. :)
Travel trailers usually have bigger tanks than truck campers, or you could mount tanks under the truck's frame, as you said. The bed is usually a good size in a trailer too, and the bathrooms are bigger. And of course the floor is already flat and 8' wide, usually with some storage compartments on the outside, which truck campers generally lack.
I would think that de-framing a trailer might lead to the total destruction of the trailer when you try to lift the body of the trailer onto the truck with no frame holding it together?
You could leave the frame mounted under the trailer, remove the suspension, cut off the tongue and bumper, and mount the trailer frame to the truck frame with square tube cross members in between, like a sill-less flatbed. Cross members needed due to the narrow truck frame, versus the wider trailer frame.
A friend in town here did something very similar, but with a pontoon bass boat and a fold out camp trailer. He stripped the boat upper section down the just the bare flat deck, removed the axle and suspension, tongue and bumper from the camp trailer. He used a forklift with extended forks to lift the camper up onto the boat deck and attached the trailer's frame rails to the cross members of the boat's deck with brackets he bolted in. Since the boat's deck frame was aluminum and the trailer's frame was steel, they couldn't be welded together.
