240z Casting Numbers

Does anyone know the significance of the casting numbers on the Driver's side on the lower portion of the engine block?

Is there a special code for day, month & year for production date? For example, on the old Pontiac GTOs of the mid & late '60s, a letter such as an "X" stood for the 24th day of the month and a "4" would indiate that the engine was made the 4th week of the month, etc.