Regular production of parts, mid February 1963.
Ford had preproduction engines in vehicles going through testing by September 1962. Parts and subassemblies unique to HP289 engines started being mass produced mid February 1963. Regular production of engine assemblies started the first work day of March 1963.
1963-64 HP289s were used in Fairlanes, Cobras, GT40s, anything Shelby, Genie sports racers, Holman-Moody racers, and several other new cars street and race on both sides of the Atlantic ocean.
From memory, Ford made and shipped about 400 engines a month March 1963 through around June 1964. The highest serial numbers I have listed was in a batch of late Cobras in the 646x range with 6469 being the highest five bolt serial number I have recorded to date.
A lot of the early engines were raced to destruction and or parted out. Finding a loose block with a serial number and assembly date before about April 12, 1963 is tough. Finding anything dated in any way before mid March 1963 is tough. Mid March 1963 onward there are generally enough loose parts around to build up a date correct engine except maybe a fuel pump. June 1963 parts are rare as production slowed for the summer break. August 1963 onward parts are not super rare except fuel pumps.
I don't remember the time of change from C3OE-E head castings to C3OE-F castings but "1963" heads were used March 1963 through part of April 1964.