They must have been milling them different over the years. I've never seen any factory production sb mopar LA head less than 64cc. Most shops only pull about .002-.005 per clean up that's barely .45-.85cc about but less than 1cc ,valve seat is about .005-.015 deep, valve face .008-.010, hard seats raise the 45/exh valve countering that. In other words it doesn't cover 4ccs.
