2006 ram 2500 mega 4x4 cummins 5 ft bed. The reason I ask is the previous owner added leaf springs in the rear end. There is zero dip in her rear end and it rides unbelievably comfortable.
I have the same truck, but lifted. One thing to think about, is just because you add extra leaf springs or air bags, still does not change the rating of your axles. Your axle rating will always be the same regardless of what you do to the suspension. Just my $.02.