The designation F4D-2 was applied to an improved version of the F4D-1
Skyray equipped with the more-powerful Pratt & Whitney J57-P-14
turbojet. It was never built.
The Aircraft of the World, William Green and Gerald Pollinger,
The American Fighter, Enzo Angelucci and Peter Bowers, Orion, 1987.
McDonnell Douglas Aircraft Since 1920: Volume 1, Rene J. Francillon,
Naval Institute Press, 1988.