Dually

I had a 2016 Ram 3500 SRW with the 3.42 (only ratio available). I just traded it for a 2018 Ram dually with Aisin and 3.73. I got the 3.73 for towing the 5th wheel. I think you will be fine with a 3.42. If you get in hills you could always lock out 6th gear if it's shifting too much. I experimented towing the 5th through Smokey Mtns., and left it in 6th gear, let it shift a lot, and never saw a change in transmission temp.
You're good to go......
add: the front Torklift tiedowns are so much easier to install on the 2018. No fish wire!! But get you a small pair of needle nose vice grips to hold the back-up plate while you start the bolt in the welded on nut. It'll make more sense when you see it.

I’ve got a 2016 Ram 3500 4x4 LB, CC, 6.7 DRW LB, GVWR 14k, Camper loaded and wet to go about 4,900 - you should have no capacity issues

3 tons

Same camper on an old Ford dually, feels good. I'm 13k GVW, probably over when loaded heavy, not sure, haven't weighed it yet. New DRW Ram would be 14k? I bet it will be a nice improvement, Good luck in your endeavor!