Coming up with a flat trailer is not really a problem. He needs a truck to pull it
through the hilly country. The V8 Crew Cab Dakota would work great in the flatlands.
Do you think it could swing it in the hilly part? (Mark? Denny?)
For what it's worth, I pulled my 6,500 lb. travel trailer (plus added junk inside, so over 7k lbs) with a 4.7 second gen Durango through there last fall. It did fine. Not like a hemi, but good enough.