Hey Tom. I just bought a Voltage 3895 that is a little over 16k# empty and grosses at 19K#. I had a SRW Dodge 1 ton diesel I had to replace after the first camping trip. The old Dodge was rated at 16K# for trailer weight.
I went with a RAM 3500 Mega Cab with the AISIN transmission and 4.10 gears. I didn't want to have any issues with pulling hills, stopping, starting, curves, etc. I'm rated for 37,500 gross combined with this truck. GTW is around 28K# with a gooseneck, 25K# with a fifthwheel. A lot more capacity than I'll need. I pay a little in lower fuel mileage with the gearing but I am very comfortable towing with it.
Your camper is probably somewhere near mine in weight and capacities.
I probably could have gotten away with 3.73 gears or the 68RFE tranny(~23K# GTW) but I have a curvy driveway with a 22* slope to it. Blowing a tranny wasn't in my plans.
I spent a lot of time thinking about the weights and capacities of the truck and decided on overkill vs. just enough.