Rock Auto is normally good about showing which cylinders are USA. All the ones I've bought from them lately have been made in China, but that is just because they didn't have what I needed in sets (USA made). I haven't had trouble with things I've bought from them. Please keep in mind, Rock Auto makes nothing nor sells anything under their name (to my knowledge). They sell cylinders made by Raybestos, Delco, etc...
Also, unless your old cylinders are worn past the point, you might be able to hone and rebuild them. Years ago there was quite a cottage industry of people re-sleeving wheel and master cylinders but I don't see many of those guys anymore.
Jon
