I have been told that the latest casting dates on 440 - 6 blocks were around 5-70 . were all the six pack engines built in two runs ? [70-71] [ excld-a12's ] if you wanted to put correct date coded exh. manifolds on a car built later than may , would they have a date when the engine was built or would they be closer to the build date ? I know things were all over the place ... does anyone have any photos of a 71 with the block and exh. manifold dates ??