How do you identify the engine on a classic Ford Mustang if it has been swapped out?

Answer 1

It's next to impossible to tell if the engine is the original one for a classic mustang..

Mustangs built before 1968 do not have the Vehicle Identification Number (VIN) stamped into the engine block. The one exception is that all "K Code" Mustangs with the 298 High Performance (Hi-Po) package had the Vehicle ID stamped into the block as a theft deterant..

However, things like later model date coded parts on an early mustang are a good sign of major repairs or of a possibly changed engine. If one sees "C7" coded parts (1967) on a 1964 1/2 vehicle it's not safe to assume the engine is "original"

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You can also check some of the cast items on the car for their casting date. You can compare the casting date to the build date of the car (on the warrentte plate). If your engine block or heads are the correct year, but were cast after the build date of the car you are fairly sure it is not original.