Block and head groove?

I had a 40 over 340 block that was O-ringed without copper head gaskets.....Not sure what gaskets they were but they were not copper. Maybe special larger fire ring for O-rings? It was a nitroused motor according to the piston condition, ie clean crowns. Machinist said Nitrous cleans the piston crowns. Sold it to the 3rd guy who looked at it, the first 2 passed because it was O-ringed...? Take the wire out...