I read the partial VIN stamp on the block as 10F1667xx. Even with being unable to read the last 2, I believe it's very safe to say that that is the original 454 for that car. The VIN stamp narrows it down to 100 cars. The chance of a previous owner somehow finding and installing a 454 with a partial VIN stamp showing the block was originally from another SS that came from the same assembly plant, and was assembled the same day as this car, would be astronomical.
The correct engine assembly date is another good thing. It's either April 1 or April 16.
The rough surface and poor stamping by the oil filter is not at all uncommon.
Dan