I am looking at cab and chassis anyways, either 3500 or 5500. Right now the truck camper I have hasn't been off the bed of the truck in over a year and a half. I looking to upgrade to a flat bed camper camper. I expect it to be around 4000 lbs wet, but it could end up being more, I know a 3500 will handle it, but my experience with an older 2500 and 3000 lb wet weight camper in more demanding terrain like Baja and mexican roads has me thinking I should consider 5500. I am aware of the insurance issues, but I am going to see if I can register the whole thing as an RV.
The new 14,000 pound GVWR Ram 3500 duallys can now carry easily 5500-6000 pounds. The Ram 5500 I looked at comes with 4.88 axles, for a camper hauler the 3.73 axles that come on the 3500 would be more than enough. And the engine on the 5500 is detuned to accommodate a better duty cycle. It does not have the 900+ foot pounds torque that the 3500 comes with. Lots of things to think about for me. I contacted Highway Products in Medford Oregon to get an idea of price for a aluminum flat bed; about $7500 starting for a basic bed. I am confident steel beds are less.
I am not sure about Utah's laws, but in some places registering the truck as an RV means the camper has to stay on the truck. Taking it off for some work at the RV dealer or taking it off to get some service done on the truck and driving the truck can be technically illegal. Since I would likely not have the camper on the truck all the time I would need to register it as commercial. I definitely like flat beds and would like the 19,000 GVWR of the 5500. Plenty of capacity to also tow a trailer and carry lots of extra stuff.
Progressive would insure the 5500 truck as long as I sent in pics showing the camper on the truck and signed an assurance that the truck would not be used as a tow truck.