Air bags will not increase the payload or Gross combine weight rating on any truck. What Air bags will do is to equalize the load carrying ability of the truck and allow some of the load to be shifted to the front axle.
As an example if the truck and trailer combination when hooked up for towing, the rear end sages and the front end of the truck is noise high. The air bags when pressurized will allow the truck to sit level with the load of the camper or any object in the bed that is causing the front end to be nose high.
What I did when I first installed my air bags was to measure the frame/rear bumper ( something that can be easily measured) to established the ride height of the truck, as shipped from the manufacture unloaded. I then attached my 5er to the truck and duplicated this dimension as I added air to the air bags to insure a level load. I recorded this air pressure and use this now to inflate the bags after I attached the 5er every time.
2016 34RL CC; 2008 Ram Mega Cab 2500HD, 6.7L, 68RFE 6 speed, 4X4, Smarty S67, TDR 135K+miles