I've seen a few of these done over the years, and honestly the biggest headache is always the frame - not the camper itself. The 80 series unibody is tough, but putting a hard-mounted camper body on it means you're creating a leveraged moment arm that the stock floorpan was never designed to handle. Every rockflex, every river crossing, every hard rut puts twisting force through mounting points that want to fold.
If you're set on going this route, the key is a full subframe that ties into the existing frame rails at multiple points - not just bolt-in plate to the floor. Something that spreads the load back toward the engine and rear diff crossmember, not just relying on the sheet metal floor. Most of the "chopped up 80 with a camper" builds I've seen that are still on the road did exactly that.
The width thing is real too. Most 4WD truck campers are built for 3/4-ton trucks with fender flare clearance. An 80 is narrower and you WILL hit trees on tight trails. That's assuming you can even fit it without the camper eating into your approach/departure angles.
If you're not married to the idea of keeping your current truck, the cab-and-chassis route the others mentioned is genuinely the better path. No compromises on frame, full payload capacity, and you can still run it hard.
