The Fiat G.56 was a fighter aircraft that combined the fuselage of the successful G.55 Centauro with a 1,750hp Daimbler Benz DB 603A to produce the fastest Italian fighter aircraft of the Second World War. The 275hp increase in power lifted the aircraft's top speed up to 426mph from the 391mph of the G.55. Two prototypes were built, making a maiden flight in German occupied northern Italy during 1944 and a second a short time later. There was always a limited supply of the DB 603 engines, and the available production was all earmarked for German designs, so the G.56 never entered production. It would have carried 3x 20mm MG-151s with provision for 2x 20mm cannons in the wings as well.

http://www.airwar.ru/image/idop/fww2/g56/g56-2.jpg http://en.valka.cz/files/g56.jpeg