Get the dually if you feel compelled to do so but it is not needed for 95% of the 5th wheel travel trailers. I make a count on trips of how many 5th wheels are pulled by trucks with DRW and with SRW and on every trip I find that more than 80% are pulled by trucks with SRW.
SRW is more than enough even with stock 17" tires for 5th wheel trailers up to 14,000 lb. loaded weight. With 19.5 rims and tires you can go to the very heaviest 5th wheel travel trailers being made.
I bought a SRW diesel 2500HD truck as I wanted the extended cab which is not available with a 3500HD truck and the only other difference was that the 3500HD had an extra set of leaf springs which I would easily duplicate with SuperSprings to get the same payload capacity.
With Ram the 2013 and later 2500 and 3500 trucks have the same frames and same towing capacity but for the leak packs, choice of tires, and gear ratios. With a gas engine powered truck I always get the lowest gears that are available. MPG is the same or better with the lower gears and when towing the rig performs much better.
Think about after you drop off the trailer at a campsite what you want to be driving around the area and exploring. The very last thing I would want is a DRW crew cab long box truck.
Don't get suckered into spending $65,000 for a truck. It is crazy and unnecessary. My current truck is a GM diesel LT trim 4WD with every option package including tow mirrors, side steps, rear camera. bed liner, entertainment package, etc. though with cloth seats and I paid $41,700 in total for it. If you walk onto a dealer's lot with the expectation that you will be paying $65,000 for a new truck I can guarantee that you will be successful and you will not be alone.