Our camper weighs about 4,000 lbs loaded. We tow a 3,500 lb boat but used to tow a 6,500 lb boat. I have a 454 engine. I have no complaints about the power of the 454. I go slower up steep hills and get 9 mpg at 65 mph, but it was $10,000 less than a comparable diesel when I bought it so I was willing to make those sacrifices. The only time I wish I had a diesel is when I get stuck behind a slow driver. I simply do not have the power to pass.
I have a dually with air bags. I have no sway and very little lean. I would also add that I have load range 'E' tires which made a big difference in sway. My previous truck had overload springs and I preferred those as they seemed stiffer and less prone to bouncing on bumpy roads at highway speeds.
P.S. I've never hauled a big camper on a single-rear wheeled truck so I can't compare. I had a dually already when I got my first camper. It's a big part of why I got a camper.
