Not much I can add here. So, anyway...
My Wilderness goes about 7500 lb loaded and I wouldn't want less truck than the 1500HD. HP not the whole story. Crew-cab essential for me. Real (air-over) oil cooler & trans cooler. 4WD. 8 lug axles. Weight ratings. 6+ ft. box. Even so, I believe this truck would be marginal in the mountains. Of course newer trucks undoubtedly make more power.
I bought my camper first, and then had to learn about big trucks (drove Nissan PU's since '84) and pick one. Was very lucky to find the HD (used).
Mostly make short tows in the flatlands, could not justify the extra expense, and it is hefty, of a Diesel.