I recently purchased a 2005 c4500 4x4, the original owner had it upfitteded with a dump body, plow and firestone air bags. when I purchased the truck they were disconnected. Used the truck for a while before I had time to look into them. I simply hooked them up to a presta air valve mounted to the subframe “simple simple” Aired them up with the compressor they leveled the truck completely reguardless of the load, truck drives like a dream. I highly suggest doing what your are thinking. This is a simple install everything can be purchased on Amazon good quality parts a little bit of your time you should be able to complete it for under 425. At the same time I would suggest replacing your shocks with a good quality set to avoid the sway of heavy load
I sold a F350 chip truck to purchase this C 4500, I had installed a set of timbren helpers on the f350. They worked great for a while I did notice the truck started sagging again overtime.
I think they are good but not nearly effective, when comparing them to the Firestone airbags.
Pasquale Tree
MA