So yall’ i Just came across this on the flatheaddrag.com. website.
A serial number for (some) Flathead blocks?
http://www.flatheaddrag.com/birthday.html
I found a number on my 1950 8BA block is XXXXX SC CAL. The pickup came from the Long Beach Ca assembly plant.
Until reading this and seeing the second similar number I thought it was from a rebuilder.
Now stamped into the left front of a 59AB block of unknown origin is KA XXXXX CAL
While the numbers do not follow the sequence stated in the article, the two are similar and the stamps are identical.
Interesting similarity.