Does your truck have a 9900lb GVW? Weigh it and find out what your base weight is. Subtract and there is your payload number. I bet your axles are rated for a little more than the GVW. Check tires for max weight. If you have a 6.5 ft bed u can put a short bed camper on it. A lot of people do. Check out turbodieselregister.com camper section.
Good Luck
Good Luck