A gasser will be fine for any TC, even at altitude. I have the rig in my signature (see several post up) and just recently did Beartooth Pass in both directions. Boondocked down some gnarly roads with careful ease. Never lacked for horsepower or torque even at 11,000'. Coming down was a piece of cake without ever worrying about the brakes due to downshifting and variable valve timing to create additional breaking. Fixing to order a dually to carry a 5,000# camper and it'll be almost identical, Ram 3500 DRW 4wd with 6.4 gas engine.