Take a look at this performance sheet. It is from a Fiat G.56 prototype test (one of the two built and succesfully tested). It was simply a re-engined G.55 (with an early DB603-A version). The G.55 was the only Serie 5 (Reggiane Re.2005, Fiat G.55 and Macchi C.205) able to mount the mighty DB603 without any major modification. No Bf109G could mount the DB603.
The fighter was ready to be built both in Italy and in Germany but large scale production never occurred due to USAF bombing of North Italy and Luftwaffe envy/blindness.
This sheet was shown for the first time on a recently published book about the never tested Re.2006 (image and web hosting courtesy of Orso of Warbirds 4° Stormo Caccia).
