I get it that normal range on the manifolds are 2-3 months ...I know there are no 6 pack blocks. hp or hp 2 does not matter .. that being said , for the people who have real 6 pack cars [ or photos ], with orig. blocks , what is the latest known casting date seen on a 6 pack block ? if they are all over the place , there must be an early and a latest known date ? I am talking what is known here. and , what are the dates on those known manifolds . fwiw, I have never seen a six pack block with a casted date past 5-70 If that's the case , then you would be able to look at the latest known six pack cars and look at the cast dates . the reason why is I hear they built most of the engines in two runs .I have no facts . it is just a little more info on how things were done . any takers ??