Dave, I have the airbags that you're talking about. I installed them to prevent sagging when I tow. I have the full Firestone system with bags,and the digital controller in the glove box.
They do act as a very mild lift, but you're only going to get about an inch out of it. In the event that your truck is squatting from a heavy load, they will lift it back up to stock height, but otherwise, you're not going to get much out of them as far as increased ride height.
Also, if you do use the bags as a lift for the rear, you're going to end up with a very stiff ride.