Help....Replacing Rear spring wiht Air Bag

[shine]

Ok Im looking to replace the rear springs of my 69 Chevy 3/4 ton with air bags. whats the cheapest way to do this? Whats the biggest bag I can use? I have looked around and saw alot of posts but im starting my own.... I really want to fab the brackets myself anyone know how I can do this? any help is appreciated. any step by step instructions or magazine articles? anything will help at this point. Im going to just chop the front springs. Im not looking for an extreme drop just want some room to play with it.