there are never any stamped numbers on these heads. all numbers and letters are raised cast. 3418915 with a 1.88" valve is 1972 340 and 1971+2 360, J head. casting dates are cast on the top of the intake port near a valve spring, abbreviated month day year, hard to see in the pics. and the guys working in the foundry did not worry about perfect markings, they were being pushed for quantity
