340 blocks and dates

I recently picked up 3 340 blocks from a retired drag racer. The price was right and I didn’t pay too much attention to any numbers on them. All three have an issue here or there but nothing major. Well, this weekend I was rearranging the disaster area masquerading as my garage and paid closer attention to these. One is June of 67, the second is May of 73, and the third is July of 73. I’m curious as to how close to the start and end of the 340 run these things are. Also, the two 73 blocks have no VIN stampings. Given how late the casting dates are, do you think they were possibly parts counter pieces?

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