Got some room in the garage finally and was looking at these again. They code to 75-79 Truck or Van 4bbls. Doing a little research lately I see some people call them Orange or Blue blocks with the Orange being stronger. Don't know if there's any truth to that? I also read a Machinist say that his machine boring tool (Whatever it is they use, I'm not an Automotive Machinist) dulls quicker when boring out 509's compared to other blocks. I believe the 010 stamp is 1% higher Nickel content, not sure what the other numbers/letters mean if anything.
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