[Theunz]

The manufactors expect 3/4 ton and one ton trucks to be used for hauling heavy loads, hence the rear biased rake. I think that they design the rear suspension to be a little softer until the springs contact the overloads, usually at about 2" of travel. Once on the overloads the truck should loose it's rake and the headlights should still be fairly level. If you are just contacting the overloads and add air bags to raise the bed off the overloads than you regain the rake and just stiffen the ride to the stiffness of the main spring pack. The truck, when empty will ride much stiffer now than one without airbags. If you are squatting an additional inch or two after contacting the overloads than you need the air bags.