The casting date is Dec. 28th of '56, the serial number code breask down to January 23. It wasn't uncommon to see an "I" stamped on these engines when it it's really suppoed to be a "1". The number on mine is stamped like that as well, with an "II" right in the middle of the number. The "H" in the code means it was originally from a '57 1/2 through 1 ton pickup with manual transmission.
