I would highly recommend the Ram 2500 with the 6.7L Cummins given the towing distances that you are intending on doing. It will tow much more effortlessly than either the Hemi or Ecoboost and get good fuel mileage doing it. They are now very quiet and the extended oil change intervals would be great for you on the road. Once you go to a diesel you will wonder why you waited so long. My truck tows our 16k fifth wheel extremely well so the Cummins would tow a 10k travel trailer with ease.
The extra cost for the diesel option will easily be made up in better fuel economy and much better resale value than the gasser. Used Ram/Cummins trucks are very desirable and bring big $.
One warning though; a larger trailer usually comes shortly after buying a new diesel pickup :B Ask me how I know ;)
