It's a 1953 thing. They were transitioning to to the full pressure engine that year and decided to also change the low oil pressure blocks to accept the same head as the full oil pressure blocks.
That seems like a waste of money to change the low oil pressure blocks for just one year, but maybe they had not yet decided to phase out the low oil pressure blocks as soon as 1954.
That’s the explanation I needed.
Would be cool to find the board’s meeting minutes from the day they finally decided to phase out an engine oiling system that had been obsolete for a decade or more.
