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Here is a pic of a 335 Series Engine; a 351C to be precise. Notice how the radiator hose attaches directly to the block as zaac pointed out:
Here is a pic of a Windsor series engine, notice how the radiator hose attaches directly to the intake manifold:
With your block being an '80 casting, it is not a 351C as they were phased out in America by 1974. It is possible it is a 351M/400, however I believe they were phased out of passenger car use by 1979, being replaced by the 351W.
While a line code of 'A' denotes a Galaxie it is also used as a generic indicator in Ford part numbering with parts that are destined for use in a wide variety of Ford offerings.
There is a possibility that the 03C was an oversight in the casting process and should have followed the format of 0C3, which would indicate a decoding date of March 3, 1980.
Count the number of valve cover bolts to see if you have either a Windsor or a 335 series; Windsors have six bolts, 335's have 8. Your block could very well be a 302 or even a 351W. Post up some pics if you steel need some clarification.
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