OP here - You all are great - thanks for the excellent analysis and information! The photo was taken in Hamburg, New York (i.e., Western New York near Lake Erie) where my Grandfather lived. Not sure of the exact year of the photo.
Pretty sure that it's an FL and the engine is a Knucklehead.
Produced in 1936 and continued through 1947.
However....I'm sure someone will correct me if I'm mistaken!
Nice pic!
If I remember correctly, the FL didn't come out til 40ish. Prior to that, it was would have been an EL, which was a 61 CI.