The serial number under No 1 injector is no help unless you go to a Ford Industrial Dealer. There is no information available to aid dating with these "S" numbers.
"FL" indicates a 1962 - 1964 Super Major engine but it could be later. The head may have been "transplanted" on an earlier block. Is the injection pump a "Minimec"? or does it have an industrial governor or even a vacuum governor?
The injector seals are the same on all engines of this type back to 1952 and the later head gasket can also be used.
Your casting code does indicate an earlier block, casting codes from June 1963 were "number/letter/number". It is unusual for these to be stamped, they were normally part of the mould and changed daily.