There was a change in pans between 1954 and 1955 on car engines and first series 55 and second series 55 in trucks. I suspect the date code of your block will be late 54, and was actually installed in a 1955 car.
Another possibility is that it was a crate engine sold much later. I have seen these. They look like 54 engines but use the later pan style.
Does yours have a single large hole in the block for the water pump or two smaller?


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