[muscle_collector]

around 1981 or 82 i bought an engine out of a guys gasser rod. it was one of the hardest thumping pontiacs i had ever heard. he said it had 12.5:1 compression and was hilbourn fuel injected. i stuck it back and it just got buried over the years. the other day a friend noticed it and got real interested in it so we cleared out around it and started looking at it. my question is on the heads it has the casting 536109 and on the flat areas above this on one side has an X and the other side has an O and what appears to be an E down lower and to the side. anyone know what they originally came on?