NO aftermarket mods (air bags, etc.) can/will change the weight ratings on the truck. As alluded to above, the most critical specs are the ratings for the rear axle and tires on your truck. It is very dangerous to exceed those capacities (even if you have people say they've done that for years and have gotten by with it). Your first step should be to load the truck up (people fuel, hitch or weights, and anything else you would travel with) and head for the nearest CAT scales. Subtract the actual rear axle weight from the GVWRR and you will have your available payload (rear axle, that is) for the truck. Here are real-world numbers on an RV not too different from what you're considering (and my 2013 Sierra 2500HD DMax which should mirror your truck's capacities).
Rear axle rating on truck: 6,200; actual: 3,080; payload: 3,120.
Dry weights on fifth wheel: 10,570; pin: 2,090; (GVWR: 13,995).
Actual fifth wheel loaded: approx. 12,600; pin: 3,060.
Weights are with a second AC over the bedroom in the front but no W/D in the closet and only a moderate load in the basement and bedroom storage. As you see, we can't load much more and be within the safety envelope. As full-timers, we are seriously considering upgrading to a 1 ton DRW in the next couple of months. As my first flight instructor used to say, "There are old pilots and there are bold pilots; there are no old, bold pilots."
Rob