Take a look at those on here who have flatbed trucks or service body trucks. going with a 4500/5500 gives you much larger brakes and a better tire/wheel selection then a 3500 but you pretty much loose a stock pickup bed option without spending tons of cash. Though from the people I have heard from, including me, those who switch to a flatbed would never go back.
That being said there are lots of folks who have campers that heavy with dually trucks. A few things are recommended. Stay within axel, wheel/tire capacity’s and upgrades to suspension (bags, sway bars).
If could do it over I would get a Ram 4500 over my Ram dually, I took my bed off and put on a flatbed about a year ago and it’s the best upgrade to the truck.