[4dblnkldude]

I am currently on the hunt for a 64 76x9 block. I'm sure there are some experts on here. The manifest is stamped May 12, 1964 and in some documentation I have found says it was built second week of May. The production date in the upper left hand corner says 05 28. I'm having trouble making light of this. What would the actual production date be? What date code should the block be? It has a 65 76x block in it now. I have the original rear that's going back in next year and wanted to make the car period correct. Thank you for any help!