Towing with a 6.4 hemi With 4:10's

Payload consideration for gas vs diesel pickup is very subjective. When talking TCs and most of all of the weight on the rear axle, just like a 5ver, and the engine pretty much all on the front axle, the only payload difference is on paper. Just food for thought.
Otherwise 6.4/4.10 combo will haul any TC smartly and will get you places with your 5ver for a year safely.
Takes a lot of snort to run a 12'x8' box down the highway. I get a little better mileage pulling a 6000lb boat with a tower or a 32' enclosed cargo trailer than I do with the camper on.

I've got the 3:73 in my 3500 SRW. My 5th weighs in at 11k dry. I'm in the NE also and very happy with the 6.4. 14k is a lot of weight, how soon do you plan on switching to a TC?

mostly east coat and new England towing the fifth wheel , looking to move to a truck camper at some point soon so that's the reason for the gas trying to get as much payload capacity as possible but may need to tow the trailer for a season before we make the change

14k is a lot for a gas truck. What part of the country would you be towing? It would be more doable east vs if you plan on coming out west.