Well, to begin with I try to be careful with money and not over buy. ( I realize tahat non Airstream owners may choke on that!) Anyway, I have an International 23 @ 6000lbs and loaded probably closer to 7000lbs. I live in the Rockies.
I bought a 4x4 Dodge 1500
with the 5.6 L engine, The diesel was 10 grand more and that represents a lot of gas. After a lot of thought I decided not to go diesel and stick with the hemi enhine which is well known and has a proven record.
With this truck, the Rockies are no more of an issue for me. I can tow my AS up a local 14% grade and even accelerate to the top. I get 20mpg and the truck has some kind of antisway mechanism built in as well as a complete towing package.
I'm happy with this combo.