There are campers for truck beds and there have been for years. Depending on the truck you might need to change the suspension for the new weight. Example of

There are campers for truck beds and there have been for years. Depending on the truck you might need to change the suspension for the new weight. Example of a camper for OHV https://vagabondoutdoors.com/product/the-drifter/ https://vagabondoutdoors.com/product/the-drifter/