20k-50k miles per year is a heckuva lot of miles to put on a gasser getting at best 10 mpg with a big camper. Lots of miles with the engine under load is really the place a diesel engine (and the emission systems) shines, but I can appreciate you wanting to go with gas. With that much seat time, I'd approach this more like you were a hotshot driver and prioritize cab and seat comfort, quality of the headlights, service intervals on engine and transmission, etc. With that much time on the road, you might want to consider driver assist features (lane keep, adaptive cruise, etc).
Ford's cab has a flat rear floor, I think that's a big advantage over the Ram cab. Ram's cab and bed is shorter than the crew cab short bed offerings form Ford/GM (6' 4" vs 6' 9"), giving it a significantly shorter wheelbase and better turn radius that could pay off in daily driver or trail situations. Watch out for issues with the center of gravity of some campers being behind the rear axle on Ram. Ford has a selectable e-locker, Chevy/GM have a G80 auto locker and Ram has a limited slip. Pick your poison there. Ford also just updated their trucks for 2023, including a new gas engine. With steps in the bumper and bedsides, it's much easier to access cargo in the Ford and GM trucks than Ram. Ford's aluminum body might be preferable over steel depending on how they treat the roads in the winter where you live.
Yeah Diesel is out for me no matter how many miles, not dealing with the diesel repairs and loss of payload. 50K would be a pretty busy travel year, 20K is more normal, I mean a trip to Alaska and back and you are over halfway there, couple of trips to the Keys and a couple of trips up the eastern seaboard and your are over 20K, so thats where I kinda ballpark the 20-50K. I currently put about 20K a year on my current truck and I don't have a daily commute so most of that is travel and trips around town etc.