Airbags help with handling but they don't increase your payload. As said above find your door sticker and subtract the weight of the truck from the GVWR. That number is your payload. You should allow 1000 pounds for stuff and passengers and you are likely to find that then there are few if any campers that your truck can carry. An upgrade to light truck tires can lend a bit more payload but not much. You can overload at your own risk and if you use the thing rarely you might be OK, but if you camp much you are slowly killing your truck's suspension system by overloading it.