F250 6.2 gas Towing heavy with 3.73 rear ??

Get the camper package on the F250 so you get F350 suspension or select the F350 as a starting point. Between truck occupants, gear and pin weight, you will want some more suspension capacity.

I would look at getting at the more capable gear set to possibly future proof the truck for an RV upgrade at some later time if you are willing to take an unloaded fuel economy hit (I don't think towing mileage will be any worse).