As others have suggested, just get a longer wheel base and mount the camper completely behind the cab and you get a nice storage space under the overhang.
That said, I don't get the idea that new trucks don't last? If you look at the facts, they last longer than they ever have. It's nothing to get 200-250k miles out of a truck. 30-40yrs ago if you hit 100k miles it was time for a new truck or an engine overhaul. The only reason I could see for moving up would be if you are exceeding the load ratings (which are higher than ever with new trucks).