He's "qualified" though.......
6,7,8 whatever. The point is it will work. Is it ideal, no, the 3.92 is better suited. The op said only occasional use. As long as he’s ok climbing the pass slower than bombing along at turbodiesel speeds he will get where he wants to go.
(I lived in Colorado for 10 years and towed a 4500# wood framed 1972 24’ trailer with a 7,000# CC 1 ton truck that had a low-rise camper on it. Never went anywhere without full tanks of water and propane cause we dry camped a lot. The truck had a GM 400 good for 210 hp/appx 310 tq and a 4 speed auto. Climbing the passes was in 2nd gear at 30-35 mph.)
Now the problem is “trailer creep” or “trailer usage creep”. He’s starting off near or at the edge of capabilities (note he indicated a 6K trailer. Is that dry weight or camping weight?) If that‘s dry weight then he may be adding 1K or more in water, food, gear, misc. not counting what‘s in his truck. If that’s trailer gvwr he still has to account for what the bed of the truck may have.
Either way his 8 speed and hemi have a lot more useable power than my old truck did but somehow we made it for years with that combination. People tend to forget that power isn’t what’s lacking with a 5th gen 1500. I’d suggest he be more careful with payload and braking.