Super Dave
I do plan on towing heavy 10 to 12 thousand lbs. I also figure a 3500 lbs camper loaded it will be at least 4000 lbs. The utility bed fully loaded with generator, tools, food, extra water and other gear could be 2500 lbs. Plus 1000 to 1200 hitch weight I would be at or over the GVWR of a 3500.
You can not get large fuel tanks from transfer flow according to their website. Nothing after 2012 from what I can see. And the 35 gallon OEM fuel tank isn't going to take me very far when fully loaded.
It also appears that the 4500 works out cheaper in the long run than the 3500. Mind you that I would be looking for a tradesmen class Ram. I'm going to be camping on the beach or in the dirt in the Sierras. No need for anything fancy.
But I would want good brakes that aren't being tested. And shocks that keep me from bouncing around.
The one tons are rated to do what I need. But are a bit under the safety factor I want. I also like the 72 gallon tank you can get on the 1 1/4 tons and up.