Not sure how much different the '47-'59 brake are then the '63. My recollection is that Chevy really didn't do much in the brake department until a bit later - but what does a Ford guy know. Page 13 of my latest Speedway Catalog (still cold from the mailbox) shows a 47-59 kit.

SS Brake Co advertises that they can fit about anything:

http://www.stainlesssteelbrakes.com/

Another is Baer and they do list a '63 kit:

http://www.baer.com/

Before I found a correct rear Wilwood kit at Speedway, Baer said that they could make up anything I needed.