Good news on the longbed. As you can see I have a 9.5 ft. Lance that weighs 2800 lbs. dry and usually about 3400 lbs. ready to camp. I pack light and tend to fill with water near where I am going to camp. I store enough water for toilet use on way. Door sticker says 2900 lbs. I have 3750 lb. tires and use lower stableloads and in my opinion I might improve only with a sway bar. I don't pull behind and that may require more mods. Truck rides slightly high in back.
Anyway, I believe that the era of campers you are looking at, you can find 8 - 9 ft. camper that will work well with what you have.