Well, I've got a 26K diesel, with a 330 turbo cummins, pulling a toad and I got around in Colorado just fine. Not fast up the mountain but I still got there. How much time will you spend going up?? Another interesting point....in the mountains, I can go up the hill, no matter how steep, faster than I can go down. Yep, the brakes are the main issue in the mountains. Been there, done that!
Diesel vs Gas. I need the diesel! However, remember the old saying if you buy the diesel, "better bring some money to town". Your gonna need it.