You are pulling our leg, right? The only thing to decide is can you sneak by with a 3500 SRW or do you need to get a dually? And how much extra does the RamBox weigh? In the past the Mega Cab had lower towing numbers because of their higher curb weight.
My vote is for a 3500 dually Quad Cab with the new 850 foot pound engine and Asian tranny.
Do it right the first time. And make sure the trailer has optional GY G614 tires or that it at least has the newer wheels rated to 3750 pounds each or you will be buying tires and WHEELS in the first year!
Chris