To do it right you'll need to know the weight of the camper, the weight of the trailer with car and everything loaded - fuel, people, gear, water, food etc. Subtract this from the GCWR of the truck. Without knowing any of the above my guess is you'll be way over the limit. It's not just springs and tires. It's transmission, engine, frame, brakes etc.
I don't think I would worry so much about engine trans and brakes, well maybe a bit with the brakes, but for them your just going to end up changing them out more often. engine and trans, towing the big trailers and 5th wheels work the engine and trans way way harder than having it loaded up with cargo to the capacity, or a little beyond. I notice it big time when towing my 5th wheel then switching to the truck camper, I can only run the 35hp tune on my truck when towing the 5th in the mountians, with the truck camper I can run a 100 hp tune. also before the tunes, I get way way better fuel milage hauling the truck camper than towing the 5th, and the trans doesnt get as warm climbing hills. And, believe it or not it, actual braking is better also.
to me the most important thing your going to hit is the limit of the tires.
It's a 21 year old truck. I'd be concerned with everything I mentioned.
