Starting in 1968 Ford began stamping partial VIN information on a pad just under the back of the driver's side cylinder head of all factory-installed 428 Cobra Jet engines to comply with Government-mandated regulations. Partial VIN stamps have also been found on cylinder heads in the area just above this pad. Service blocks didn't receive VIN stampings, so as engine swaps have taken place over time it has become very difficult to keep up with this "matching numbers" reality. Once an engine is installed it's practically impossible to see this stamping even if it does exist! Ford also stamped partial VINs on transmission cases, so take a peek at when you next have a chance.