The best answer to this question is "usually not". Many factors could cause a discrepancy between a scheduled build date and an actual assembly date, such as shortages of parts, worker strikes, and any number of other things. From what we've seen, the actual assembly date tends to differ from the scheduled build date. As an example, we know that the scheduled build date for the start of 1969 model year production at the Dearborn, Metuchen, and San Jose assembly plants was "04G", or July 4, 1968.

There's a common misconception that the 5th character in the Vehicle Identification Number (VIN) can be used to determine if a car is equipped with a Cobra Jet (CJ) or Super Cobra Jet (SCJ) engine. The myth is that Q-codes are CJs and R-codes are SCJs. In truth, these codes identify the type of induction system installed during factory assembly. 1969 - 1970 428 CJs and SCJs that were equipped with standard air cleaners are identified by the letter "Q". Ram air induction is identified by the letter "R".