One of the great WW2 "What If" stories involved the modification of the excellent Italian Fiat G.55 Centauro into the Luftwaffe-approved G.56. Goering informed Hitler of the potential of the G.55 and so a licensing agreement was made for Germany to produce the plane in 1943. However, with the Italian Armistice this agreement was cancelled and the Germans could only get 105 G.55 Centauros built before the collapse of northern Italy with Italian fascist help. To meet German standards, the G.55 was modified into the G.56 which would use the 1750 hp DB 603A engine instead of the DB 605 and then steadily increase the hp by model of engine up to anywhere from 2660 hp-2800 hp with the DB 603LA. Speed with the 603A was 422 mph, ceiling of 42,650 ft, and range of nearly 750 miles armed with 3x 20mm MG-151/20s!!! And this was BEFORE the escort fighters arrived in Europe. It could have been a formidible warplane and Germany's third main fighter after the Bf 109 and Fw-190 series. However, being realistic, the Germans would have made even more modifications to the cockpit, wings, control surfaces, etc... and getting the DB 603 series going was already troubling. So it is questionable at best. The latter Bf 109G and K series as well as the Fw-190D series and Ta 152 were more than a match for the Allied fighters of '44-45 but were heavily outnumbered and suffered delays in production and repair due to round the clock bombing. Still, the idea of a German G.56 is always thrilling! The Italians also would have had a formidible jet fighter in the Regianne Re.2007 with German jet engine and German armament- the protitype was under component construction when captured and still waiting on German Jumo engines that never arrived but were intercepted and sold for scrap!!!

http://upload.wikimedia.org/wikipedia/commons/2/2b/Fiat_G.56.jpg