I had the same trailer prior to my new trailer and truck. I also pulled it with a crew cab hemi. I had stepped up to the hemi from at Chevy 1500 with the 5.3 I believe... I was impressed going to the hemi, it pulled it well. It rev'd a little harder in the hills then I really cared for, but it would do it all day and not hiccup once. The hemi is a great motor and the 26DBH is a great camper.
After a few shorter trips with the 1500 Hemi I noticed my trans and engine warming up fast, never got to where I felt uncomfortably hot, but it would heat up fast going up hills and such. This is mainly due to the drive train and cooling systems being smaller.
I switched to a 2500 for the added weight to help "boss" the trailer around rather than being the other way. It also gave me added confidence knowing my drive train and cooling systems were built for the task at hand.
Seeing that you will be in the mountains often, I highly recommend the 2500. This will give you a heavier truck for added control. Steering will be beefier, tires stiffer, cooling systems bigger, brakes bigger and drive train much stronger.
The newer body style rams 1500/2500/3500 all ride very nicely! If you can afford a cummins DO IT! you wont regret it! If you do go with a Cummins try to get a 2012 as it wasn't mandatory to have the DEF (Diesel Exhaust Fluid) added to it yet. This is just another task and thing to remember, it will also up your resale as people a few years from now wont want to deal with it!!!
As stated earlier... Buy the most you can afford now... I have gone through 3 trucks in the past 1.5 years stepping up... (dont tell my wife, but I still wish I would have bought a 3500 manual transmission