Regards to the truck question "will my truck pull it? or how much truck do I need to pull it" - the real question is how much truck will I need to STOP it. Remember the Toyota Tundra pulling the Space Shuttle. A 1/2 ton pickup will pull a 747 or locomotive engine but the real question is will it stop it. Remember brakes on the RV may not be adjusted properly or may fail. In my mind it is better to go with too much than not enough. MHO
I'm not sure about Ford or GM, but the Ram 2500 and 3500 (at least the year that I own, a 2012) the ONLY difference between them is the rear springs as far as payload and towing goes. The engine, transmission, drive shafts, transfer case, brakes are all identical. (and a pair of Firestone air bags will MORE than make up the difference in the springs)