Air bags will help to level the truck. It will not increase the gvwr of the vehicle. The tires, springs, shocks, rear differential, ujoints, transmission and engine all combine to make the system that allows a certain weight to be carried and towed by a vehicle.
Each piece of that puzzle set the payload rates for that vehicle. The tires have a payload rate. The springs have a rating. Each component has an individual rating. The vehicles GVWR is set based on the weakest component.
The best advise has already been suggested. Weigh the tow vehicle. Weigh the trailer. Weigh the combination. Then and only then can you make an educated decision as to your options. Good luck. Happy camping.