Your actual payload rating won’t change even after installing the modifications you mentioned. It will help with how well it can haul a camper, but that’s it.
What camper are you thinking about getting? With your modified Power Wagon I wouldn’t put anything larger than a Lance 650 or Capri Retreat on it. The ideal match would be a pop-up camper like the Four Wheel Camper Hawk, the Alaskan 6.5, or the Bundutec Wild.