RE: ram 1500
I hauled a 30ft travel trailer loaded withmy 04'1500 (5.7 hemi) with no problems( motor had no mods). Gas milage sucks but then again it was never that great in the truck. In terms of off road my 99' chev with diff lock was very impressive, the dodge not as much but really depends on tires and driver. My wife had a hard time sticking the chevy. In terms of pullingthe chevy wouldn't cut the mustard on a heavy haul like a 30' trailer, 5.3L.
For work Iuse a 06' 3500 Ram 5.9 cummins, 6spd manual it haulswith ease. Prior I had a 05' F350 6.0L crew, it was a misery. Loved the room, good off road but power wasn't great under heavy loads, not to mention it spent far to much time in the shop. Both trucks had no mods for fear of something happening and losing income!
I still havemy 04' ram it has seen some mods now, slight lift, chip, intake, exhaust, lockers and open country MT's. It is my hunting rig and never had a problem with any terrain. In fact the truck hasn't seen the shop to much beside routine maintenance. It'll haulthe bob and trailer but not as effeciently or effortlessly as the deisel.
If your hauling only once a year the 1500 5.7 will do it, but the 3500 TD will do it easier. I don't think I'd buy an MDS one though, heard stories about them not being up to snuff. Off road the desiels can be both good and bad, the extra weight can be both friendly and foe...if you can drive you should be ok. MY opinion is if you buy a diesel then don't buy the expensive MT tires, they chew threw tires more so then a gas. Also I wouldn't want a dually for offroad, they are haulers and thats about it!