I've never seen a source for the ending number for 1953 I8 engines, but you could estimate the lowest number it could be by taking the starting number for 1953 and adding the series 40 production to it:
starting I8 sequential number for 1953 = 6,950,620
1953 Series 40 production = 217,674
So at a minimum it would be 7,168,294, but they always built extra for use as replacement engines, etc.