Generally there is a data plate on the firewall. If that is unavailable then you can look on the block under the exaust manifold, the number is sometimes there as well. If all else fails you may be able to get information fom a ford dealership, or at least pointed in the right direction. the car is not as valuable if the numbers do not match. Most likely it is from the car being repaired, using used parts. Good luck, and great choice for a car, '65 is badass.