BP is either a 3.08 (1967), or 2.73 (1968 and 1969) non-posi 10 bolt. Yours was assembled April 7th on the night shift, but you 'll need to find the casting date to know which year. However, I highly doubt an early April axle would be installed in an early December car.
Note that BP was also used on the 1965 Nova (3.07 10 bolt non-posi)
Ed