I've been hauling my 6x10 enclosed trailer with my 2012 F350 6.2 gasser reg cab/long bed with dump insert for about two years now. I am looking to get a 8.5x20 so that I can haul two Walkers, the 36inch Scag, push blower, backpack blowers, trimmers, fuel etc.
I think my truck will get the job done but I would love to take on the task with a diesel F450/550 dump truck.
As is now, I don't get great mpg's while hauling the 6x10 with a single Walker and all the other stuff. We make lots of stops and starts, the set up gets about 10.5-11mpg's around town.
Empty with no dump insert and not hauling anything the truck would get me around 13/15mpg's between city & highway driving.
I am considering upgrading to a bigger truck next year, this year has to treat me well first through!
FYI: I liked the mpg's I got with my 03' Reg Cab/Long Bed Silverado 5.3 4x4. The transmission started to get sloppy when it hit 125,000miles and the suspension would drag ass nearly everywhere. Throw a couple yards of mulch in the bed with the trailer hooked up and it was anything but safe or professional looking. The stopping distance was dangerous. Now with the F350 I can throw 3yards of soaked loam in the bed-hook the trailer up and have no issues. It was the right move to make.
If I could do it over again, I would go with a dually rear set up to spread out tire wear.
Good luck hunting!