I have many, many factory grinds in my files, but I'll post this one because it is one of my cars. The entire pad was ground off this 16,000 mile car and it received 100% on the pad surface and stamps at judging. It was determined the build and VIN stamps were factory correct, therefore the surface was factory ground due to an error or change in configuration. You can clearly see where the bottom portion of the entire pad was ground completely off and the ridge close to the block where the grinder could not reach.

My brother's Black 73 L82 survivor also has a factory grind out, it has 30k miles & never had the heads off. When I inspected the car I noted the grind out, it didn't concern me much and didn't cause my brother to hesitate in his purchase.
When on display at the NCRS national show a couple of judges looked at it and agreed it is the original engine with a grindout.