JC, if you are not concerned with 100% correctness then you can get a master cylinder from your local NAPA store that is the correct shape as original. It does not have the bleeder screws, casting number, or the small machined pad at the front where the US stamp was at, but otherwise looks correct. I have only found this master cylinder at NAPA as the rest of the parts chains have gone to a style that functions correctly but does not look anything like the original one.
There are a couple of good places to get your booster redone. Steve Gregori in Sanger CA does an oustanding job and you can contact him at
www.brakeboosters.com for more info. Also Jerry MacNeish does them and his look just as good. Check out
www.z28camaro.com for more from him.
I will email you some pictures of the NAPA master cylinder in a little while along with a part number...................RatPack...........