I have considered Hellwig helper springs for my 83 C20. I prefer no air lines, leaking bags, etc. to deal with. I believe that all of the supplemental springs do not increase vehicle GVWR, but the air bags might improve ride quality. My interest in these springs is for load leveling in the rear when loaded to the max.
I have read that these Hellwig springs do not affect existing ride quality since the helper springs are only employed when under a significant load.
http://www.sdtrucksprings.com/index....oducts_id=5658