Best truck to pull loaded four-horse trailer?

I think you are making a bad decision not wanting a deisel. they get better mielage, and theres a huge torque difference. If you dont want a Desiel, i would look for a Gas chevy 3500 with an Allison because if you pull alot, you will probably replace a transmission after a while. I think they made gasers with allisons, im not sure, do some research. But stay away from the older dodges because they really had problems especially pulling stuff as heavy as a loaded trailer.