Air bags can work if you fiddle with the air pressure for each road surface application. But, you will always get a 'rebound' effect with the bags. You increase the air pressure in one momentarily on the upswing and there is an almost equal but opposite pressure release the other way. It's Newtonian Physics. With coil springs we call it recoil. Only dumb old leaf springs have little recoil/rebound as the friction between the leaves molifies the rebound effect.
Arguably the best suspension for heavy loads on a pick up truck is the multi-leaf pack with many thinner leaves, not a few thick ones. If long enough, leaf springs will deliver a pretty good ride also, especially with multi upper overloads (secondaries). This is what I've done and gotten there by trial-and-error on many 4WD's. Look at the suspension on the WWII Jeeps. Many narrow, thin leaves. The Allies got a lot of mileage out of those ubiquitous critters. 4WD's up to about 1970 had a multi-leaf set up. About 20 yrs ago they experimented with a mono-leaf or two-leaf spring set up on the rear axle. Complete, dismal failure, IMHO. The only good thing was it was cheaper to blacksmith one leaf.
Search back on the TC forum for suspension upgrade ideas.
I see you are in Durango. I think this little guy lives down in the engine house:
jefe
'01.5 Dodge 2500 4x4, CTD, Qcab, SB, NV5600, 241HD, 4.10's, Dana 70/TruTrac; Dana 80/ TruTrac, Spintec hub conversion, H.D. susp, 315/75R16's on 7.5" and 10" wide steel wheels, Vulcan big line, Warn M15K winch '98 Lance Lite 165s, 8' 6" X-cab, 200w Solar