[VA72C10]

If you have a trailing arm rear, you simply can bolt bags in place of the springs, install schraeder valves, and fill them to ride at the 4-6" drop. Then you could adjust it if you ever had a load to haul by adding air and then after hauling let some air out...So just the cost of the bags and valves.

The real expense is in the air management and valves if you plan on adjusting the bags often. Compressor (s), valves or valve manifold, air tank, fittings, lines, gauges, controller....ads up in a hurry.