Never seen a warranty block that pre-dates the receipient car's assembly date but yours does. The casting date is coincidentally close to perfect for your car. Odd thing is casting date of 12/09/67 was a Saturday but it is a full week before the car assy. date. My Arlington z24 block was cast on k-7-7, assembled on 12-05-67 and installed in a 12B body. Datewise, yours is tighter than that but works.