Air-Bag It?? Better Suspension What Works??

[70'sKool]

Looking for proven suspension mods for my 1985 C-30 single cab dually axle ramp truck. Weight with no vehicle in tow 8140 lbs. The Firestone R4Tech Air Suspension appeared to be ahead of it's time in design and function but costly is no longer manufactured. (http://www.trailerlife.com/trailer-h...sion-system-2/)

Looking for idea's for real working improved suspension upgrades front and rear specifically for square body chevy c-30 one ton dually axle 1985. Anyone have a custom built suspension willing to share their design??