Judging by the amount of corrosion and pitting on the deck under the head gasket, I'd say it has not been decked and restamped. IF it was, I'd think the surface would be smoother. You could also measure the height of the head locating pin from the deck and compare to another block that is known to be original. I would think the machining process at Tonawanda would keep those hole depths within .002.
Verne