I'n not sure which cars interchange with which, but in general many GM parts are interchangeable. I bought the whole setup- spindles, rotors, calipers, booster, proportion valve, and master cylinder together, so they all matched each other, and they all bolted up fine to my bird.
I bought the setup from GM Sports Salvage in San Jose, California, and they did know what would fit what. I forget the years, but I think they said both A-bodies and X-body brake systems could work. I'm sure they could advise you, and if you don't want to buy from them you shouldn't have a problem finding a booster once you know what will fit. However, keep in mind what Scott said about the pins, if you are going to mix a chevy booster with a firebird master cylinder. Its probably best to get them as a matched set if possible.