I think you need to find "any" camper. There are ones that are very big/heavy now. I'm assuming you are talking about a 3500 DRW not SRW.
Other than range and pulling mtns/elevation, I believe a gasoline engine either 6.0 or 8.1 will be ok. I had a Chevy 2500 with 6.0 and pulled a 4000 lb boat with it. It had enough power with 3.73s. No, it didn't pull like a diesel, but it was a simpler engine. I think a TC will be fine. Bonus for a GM is that they are a little more comfortable, but I feel 2005 and above Ford will have better brakes. YMMV.
As far as older Dodges not rusting any more as other brands, I don't agree. Most of the time, the rumors that many people have are somewhat true. Ram has improved the past 8 years or so. A lot of people prefer the Ford Interiors/transmission and given a diesel choice would take a Cummins in that era. If you are talking as much as other brands that don't see salt or winter deicer, then I would agree.