On the HD trucks, Firestone sells two versions: One version sits under the frame rail and replaces the jounce stop - This is used for setups with goose neck or fifth wheel hardware. The better setup bolts to the outboard side of the frame rail - This gives you a wider support stance and more axle to frame clearance. I do not know if this is an option with the light duty trucks or you only have one choice.
I found if I inflated my airbags to the point where my overload springs did not engage, the ride quality would wallow on the bags. You need to keep the metal engaged and just help the sag with the bags. If this setup creates an unlevel ride, you need more preload in your stock suspension by using blocks or wedges to engage your overloads sooner.
