The Stovebolt Site Forums The Shop Area General Truck Talk Truck v.i.n. question

From 1957 onwards the engine ID had no date and no serial number. There was no engine (serial) number. The engine ID would have useless as a vehicle ID.

You'd want a unique number. The easiest way to do that is to have at least a year code and a unique sequence/serial number (as Chevrolet had on earlier year engines, and, of course, on the cab Vehicle ID).