Yes, I agree there is some confusion. But it's only because some people don't know the proper terms for these things.
The "helper springs" are what you are looking for. They sit "piggyback" on the leaf springs and don't engage until the truck is loaded.
The "torsion springs" are the axle wrap preventers. Not what you want.
Heli and many others have used airbags with success. Here's one of Heli's threads about it.
Firestone Riderite airbags installed!!!