Help with wheels and tires.

With my lance fully loaded I knew it was there but never felt unsafe to me. I have bilstien shocks on all 4 corners, biggest roadmaster sway bar and airbags with on board air. I know I will be overloaded as when I scaled it for hunting it was a little over 10k. The lance has a floor plan of 8'11'". If I was to get a dually would it need any mods? I don't want a new truck as mine is paid off real soon.

Yur actually considering putting a camper with a 9 foot floor length on a 6 foot bed?
Your name says it all. That camper is waaayyy too much for your 2500HD. You need to reconsider the purchase or at the very least upgrade to a dually. In stock form that truck, depending on cab and options had somewhere around 1800 pounds of real world payload capacity. BT,DT and have the scars to prove it. It is simply put not enough truck.
Never let the terms like "Dry" or "shipping" weights fool you. They are misleading at best and downright dangerous at worst. The only time you will ever see that number is in some engineers imagination. Add any options, some water, food, clothes to the camper and you will skyrocket in weights to far closer to GVWR than dry.