Payload needs first. Then choose drive train to what will work best for you.
If you will be above 5000' elevation ALOT, then frankly, look for a forced induction motor, be it gas or diesel. The turbo gets you to around 10,000 feet elevation or there about with out losing HP. Where as a non turbo, you're losing 2-3% per 1000' above sea level you are.
For what it is worth, a 1500 could tow what you are looking at. If you are were like me, have a family of 6, with 4 adult sized teens, 1300 lbs of people weight, throw in son other fun stuff, you would need at minimum, a SW 35 series truck to tow a 7000 lb trailer, and stay within payload of the truck.
Marty