I know the casting number on the block was 64. I have had the top end of the motor apart for a cam change air head me never checked what casting numbers is on the heads. Do you think the 1.88 intake 1.60 valve heads would be to much? I don't know the true bore size since it might be bored over. But if I get 1.88 heads then later I could use them on the 360 to keep the velocity up.