Attention: TDR Forum Junkies 
Well gents here is my lessons learned...
Firestone makes 2 Airbag kits for the 3500 and Airlift makes one kit. Obtained all of them, None of the kits will work on a 01. 5 with contact overloads without something being modified.
Firestone Kit W21-760-2220 mounts inboard of the spring pack, the bag sits on a mount on top of the "leg" on the rear lift blocks, with the mount also attached to the axle. The top mount is located where the bump stop is so this must be removed. The problem is with rear disc brakes the axle mount needs to be where the brake line is attached. This is a nice kit, you can keep the overloads but must remove bump stop (no big deal) and relocated brake lines.
Firestone Kit W21-760-2071 mounts on top of the spring pack, you have two choices remove the contact overload or cut up the bed. . no brainer here
Airlift Kit 57215 has the same problem as the second Firestone Kit.
I went with the Firestone 2071, this kit only requires 7. 5" between frame and tire, the Airlift needs 8", with my gooseneck mount there is only 8. 25" between so not much room for the tires to squat under a load.
After removing the overload installation is very straight forward. The only real problem was the bag of hardware was not complete but I had the washers and nuts required. I also recommend having a 3/8-16 tap and die available as some of the long bolts and nuts had dinged threads from banging around in the box with the heavy mounts. All hardware is 3/8-16 so all you need is a couple 9/16 wrenches and socket. Be Very Careful drilling the forward mounting holes on drivers side, the brake line runs right between the holes. Not counting removing the overloads the airbag installation took about 90min per side.
Firestone makes 2 Airbag kits for the 3500 and Airlift makes one kit. Obtained all of them, None of the kits will work on a 01. 5 with contact overloads without something being modified.
Firestone Kit W21-760-2220 mounts inboard of the spring pack, the bag sits on a mount on top of the "leg" on the rear lift blocks, with the mount also attached to the axle. The top mount is located where the bump stop is so this must be removed. The problem is with rear disc brakes the axle mount needs to be where the brake line is attached. This is a nice kit, you can keep the overloads but must remove bump stop (no big deal) and relocated brake lines.
Firestone Kit W21-760-2071 mounts on top of the spring pack, you have two choices remove the contact overload or cut up the bed. . no brainer here
Airlift Kit 57215 has the same problem as the second Firestone Kit.
I went with the Firestone 2071, this kit only requires 7. 5" between frame and tire, the Airlift needs 8", with my gooseneck mount there is only 8. 25" between so not much room for the tires to squat under a load.
After removing the overload installation is very straight forward. The only real problem was the bag of hardware was not complete but I had the washers and nuts required. I also recommend having a 3/8-16 tap and die available as some of the long bolts and nuts had dinged threads from banging around in the box with the heavy mounts. All hardware is 3/8-16 so all you need is a couple 9/16 wrenches and socket. Be Very Careful drilling the forward mounting holes on drivers side, the brake line runs right between the holes. Not counting removing the overloads the airbag installation took about 90min per side.
and then when I have the camper or a load on baord, I can bring up the airbags at the flick of two switches upto about 60psi both sides. A stable and reasonably comfortable ride when empty but definitely no way near as "firm" without... . 
