Head Help

To ID the heads you will see a X cast into the head. The big advantage to the X head was that it had 2.02 intake valves vs the J head 1.88 valve. They both had 1.60 exhausts. I don't know the stock flow numbers off hand but they were the same. There is an O head which should have the same last casting #s: 915 which also had the 2.02 intake valves.