[TimG]

A five month spread between casting date and assembly date is a pretty big spread. This kind of spread is more acceptable in a 1968 production vehicle due to a strike at the casting foundry. The more high performance the engine, the slower the turn over and the more time that is acceptable between the two dates. A four bolt main big block was a much slower mover than a two bolt main 396 block. Better the spread be between the casting date and assembly date rather than the assembly date and production date of the car. GM did not let completed engines sit around long unless they were sent back for a repair.