Lowering and raising the rear leafs

[87Bob]

I believe it was on the TV show Trucks awhile the did a suspension upgrade on a Blue oval I think it was on a dually. They took off the rear shackle and replaced it with a air bag unit. When it was aired up it would raise the rear of the truck for a towing situtation. When aired down it lowered the rear end. Does anyone know what the company was that made that? I like to get a 2/4lowering on my 85 but I still want to be able to tow a car trailer or haul a load when I want to.