New(er) Dodge aka Ram trucks.

I would be looking at re-doing your old truck.
Newer ones the mileage is just horrid.
Just got back from a 1500 mile trip, pulling a car trailer.
2017 3500 6.4 10 mpg.
The truck gets the same mpg empty or pulling a load, must be the 4.10 gears.
Plus gas vs diesel. I've hauled my buddies 28 or 30' camp trailer loaded freeway to winding roads doing 70 and getting 14-18