340 Engine with long time between casting and engine date

The casting numbers on my 340 in my 1972 Duster are "1 21 71'; signifying a casting date of January 21st, 1971. The stamping on the front of the engine block has; "33790169"; which I interrupt is December 2, 1971 on the Chrysler 10,000 day calendar. The VIN decoder for the fender tag says vehicle was scheduled for production on December 8th, 1971. So the last two dates make sense.

Would it be possible for an engine block be in the manufacturing system for almost a year? What would be a logical reason for this?

A clue may be an upside down "A" stamped on the front engine ID pad. I think this signifies a 0.020" overbore.

All of the VINs on the IP, the fender tag, the radiator support and the engine at the oil pan match. The engine at oil pan pad has the cutter path clearly defined. I have not looked for the transmission or the rear parcel shelf numbers yet.