NEW Dodge 2013 Ram 3500 4x4 -> ride is horrible! What to do?

http://kelderman.com/dodge_ram_2500_3500_4_link_rear_air_suspension

If you aren't willing to drop the dough on the Kelderman, I'm really happy with my Sulastic Shackles Those however primarily remove harshness. They won't make stiff springs become soft.

You could also talk with a spring shop about removing a leaf spring. You will lose some carrying capacity doing this, but maybe you have more than you need?