98 Expedition Lift w/bags

Would it be possible to lift an Expedition with air bags in the rear instead of using the springs. The Expos have coil springs all around and would like to know how hard it would be to use a large bag to lift the rear 3/4 inches instead of the coils. The only real company that makes a good, simple kit that I like is Fabtech-3.5". I want to use those parts and swap in some bags. So, is it possible. Has anyone tried this or am I dreaming????