Bart - the problem with the untagged B (BC, BV) from my point is trying to assure that the customer gets the correct parts (did you know there as least THREE different tensioned springs for the power valve)? Probably trying to be TOO correct for what I consider to be one of worst downdraft carburetors ever made in the USA (there are quite a few imports that are worse;) ), but we have spent decades perfecting our rebuilding kits, and I truly dislike selling a customer something that I am not sure is correct.
By the way, a few years ago, I finally found a legitimate use for a Rochester B (actually 2 of them)

Jon.