I'd reconsider getting a manual transmission for plowing. With those duals you will likely need a 9' - at the very least 8'6" plow. What size came with that Ram? Also, with a flatbed the rear end is going to be pretty light - you're going to need plenty of ballast. I have about the same setup and find an empty 900+ lb Vbox about the right amount.
My current boss is a 7'6'' but thinking about going to the 9'2'' V if i get the truck. The reason for the 4 speed is that i have never had trans problems with them. The truck has been taken care of I think that I will buy it. Thanks Ben