If you are buying new then make a requirement of your test drive, not a dozen different vehicles but when you're relatively sure what you want, to hook up your camper, loaded, and go tug it up a hill somewhere.
Any dealer worth their salt will let you do this to make a sale on a high profit margin pickup.
That said, I'd look for the bigger engine in any of the brands. 6.0 or 6.2 Chevy. Eco boost ford. I'm underwhelmed with fords 6.2. Or at least the 5.7 in a Ram.
Ram is coming out with a small diesel in their Half tons but they'll be expensive I'm sure and I wouldn't want a first year model if I planned on driving it into the ground.
If you're really going to be pulling several long trips a year a 250/2500 model is not a bad choice. The heavier chassis and suspension makes the job easier for the driver. But a half ton is ok. You're used to that and it works for you now.