52-mobil That looks like 261 green paint,doesn't "mean" anything once that head gasket is taken off look for 261 vent holes six of them between cylinders. If you have those that is the wrong head gasket, also look for captains bars and large full floq oil filter holes on the drivers side. The head could be the wrong one too if not drilled for those vent holes. Read on stovebolt how to recognize all of that,if 261 3 3/4 inch bores or bigger.