Engine was made in March 1974 from the Code Number (7403). I have never seen one with BOTH a code and serial number. Are you sure what you listed as a serial number is not the Code Number of a Short Block that may have been installed? The 19 in the Model number tells you it is 19 CID, a little over 300 CC's. The "0" is the basic engine series. The 4 tells you it is a horizontal crankshaft engine with a Flo-Jet carb. The "5" tells you it is a 6 to 1 gear reduction PTO. The "2" tells you it has a rewind rope starter.