The "B" in your engine code (it's not a serial number, that ended in 1956) was used from 1957 through 1962 in Passenger cars with the Powerglide transmission.
It's very strange that your block was cast on October 13th and machined and built on October 14th. The only way this would make sense to me is if in 1960 they skipped the letter I (eye) in the casting process making J actually September.
Mike B
