3.73's

I have 4.10's in a gas and when it goes into direct (1:1) while towing, the rpm is too high. I know if I had the 3.55's the truck would settle to 2700 rpm at 60mph which is more tolerable than 3300 rpm. This is based on towing at almost 14,000 pound combined weight (26 foot holiday trailer, QuadCab 1500 Ram). My normal towing scenario is an open car hauler and that combined weight is 10,500 pounds and the truck easily tows in overdrive (360 Magnum). With 3.55's I would be able to use 3rd gear on the hills more to maintain speed without screaming the piss out of it.

You're getting the 8 speed LCV transmission which is a big advantage and it can work it's way around the 3.73's. Also, the 6.4 has almost 100 lb/ft on my 360 so that engine will just play with 3.73's. You will thank yourself when empty with the 3.73's which is about 90% of the time in a pickup truck.

You have answered your own question with the V10 in your Class A: I have the same setup and am impressed with the Ford V10 (about 19,500 pounds).

Your diesel is worth a lot of money. If you are getting rid of it because of the PIA they are to own, I get it. I would never go back to diesel. The big bills are coming on your Cummins (injection pump, injectors, lift pump), so now is a good time to get rid of it.