I have been checking out ebay for a seal for my 56 235 and found a seller that had a bit of information about the subject. According to him the neoprene seal was introduced in 1956 and all previous years came with the rope seal. The machining tolerences on the pre 56 were different so the neoprene may or may not seal properly. The ebay number is 8051264644 if you want to read it for yourself.
