Dottie,
My former SM mechanic son tells me the 750 (black) top hat cams will work in my 403A, but it can't use the flexi-knit cams -- I bought some off an ebay auction for a pretty low price (don't remember what it was), just that it was low. The Top Hat cams in black are pretty much available on ebay! Good luck with your machine! Oh, I've got to go -- I have to trek 15 miles into town to get my son from his work -- it's time for me to leave now!
Jeanette