Which Spring Enhancement for Ram 3500 hd DRW crewcab longbed

06 Dodge 3500 single rear wheel - camper loaded = door sticker max weights - We have Firestone air springs - I've tried lower air pressure to let the rear suspension actually touch the "overload" spring - there is maybe less sway but more harshness in the ride. I run more air spring pressure to level the vehicle, and have better dampers (Rancho 9000) which I adjust to "highest" setting.

I'm saving up for a Kenworth, and I'm going to run single rear wheels on it.