Well, now that I think about it.. My brother in-law's parents pulled a 28 foot travel trailer with a slide from Oregon to Tennessee (and back) with a 1996 Dodge 2500 Cummins diesel a couple of years ago. The truck had 260,000 on it when they made that trip. It didn't so much as hiccup the whole trip. They said it pulled the Rockies with no problems at all. As I recall, when they left Tennessee they pulled the trailer to Florida and then made a wining drive back to Oregon. I think they were on the road for the best part of that summer and the truck did just fine. I noticed that it did have a little rust on it but, was apparently very reliable.
I'm talking myself into a diesel truck..