Hello.
How many miles on your truck? Maybe you're just due for some new shocks? How about tires, how old, and what are you airing them up to?
Check tire PSI, and do the bounce test on both front and back of vehicle. If your vehicle bounces more than once with this shock test, your shocks are shot.
A rear air bag suspension can be implemented, such as Firestone Ride Rite, and not inflated to too high a pressure, but there has to be a minimum inflation. 30 PSI is not that hard, should not negligibly alter ride height, and will improve stability, making the vehicle feel less like you're in some boat rocking out on the water, or a rocking horse.
I have them on my '97 and noted much better stability right off the bat within the very first 2 minute test ride.
Don't automatically assume air bags ruin a ride quality, my 1994 Lincoln Town Car had them on back, and that car rode like a dream. Best riding car I ever owned in this life.
The primary suspension on all vehicles is the tires. Tire make-model, their age, their inflation all plays a part.
Many tires turn to crap in short order, in as little as 5-10K and as far as tires like (advertised with the Big Blimp) I don't think I'll ever buy another such branded tire in this lifetime on any vehicle. They're junk.
