Since this is your first RV, I assume 7200 pounds is a dry weight estimate of some RVs you have found. There are many half tons that can pull that weight, but you need to look at all the truck specificatinos not just tow rating.
For a bumper pull, you will be closer to 8k loaded with 1000-1110 pounds of TW. If that is a 5th wheel, then I estimate that is closer to 1600 pounds of pin weight plus a 250 pound hitch in the bed. There are not many half tons that can support 1850 pounds of pin weight plus other gear in bed and people in cab. There are some more that can support 1100 pounds of tongue weight plus bed full of gear and cab, but that is borderline.
Since you mention mountains, then a forced induction engine will perform better than naturally aspirated. Fuel type matters less than torque per $ you want to spend. Are you willing to have the engine turn at 4000-5000rpm at times? If not, get forced induction.