NAPA was the only place that even seem interested in researching the brake parts for my 49, 4400. I was lucky and happened upon an older guy that really wanted to help. I had a master cylinder kit delivered overnight and he told me all the other parts were available. I first tried O'Reilys, but the youngsters at the counter gave me a blank stare when I told them what I needed. My 49 has the Thriftmaster engine. Good luck.
