Basic misunderstanding happening here. The first letter in the engine serial number indicates the production plant. So "F" stands for "Flint". The next two numbers are usually the month of production, the next 2 numbers the day of the month and finally the last one, two, or three letters indicate the engine application.
The list at the chuckthetruck site is only using the engine app
letters at the end of the serial numbers, so try to accurately determine your letters at the end of your serial number and search the 70' years at that site.
