The U.S. Centennial of Flight Commission produced an extensive history of Grumman, Post World War II to 1994.
The model year dates are similar to automobile year models, in that new year production began in the fall of the previous year (September), so there are some that were registered by the FAA during the Fall of the year before the manufacturer's model year, and may show on FAA records to be the earlier calendar year, rather than the model year the manufacturer claims. This becomes less and less important as the planes age, but can be confusing when someone offers a "1975 Cheetah" for sale, when Grumman says that 1976 was the first model year for the Cheetah.
The serial number database above was taken from the manufacturing records, and should be helpful in overcoming disputes about "what year IS it?", when comparing planes.