I heard (from my Ford GT contacts) that the car went between 208 and 212 on each of several runs at Nardo. But SVT learned from their 1999 Cobra horsepower fiasco, so they "certified" the car with a 205 mph top speed, knowing that every GT (under normal driving condition -- meaning no hills or head winds) will easily achieve it.
BTW, I've also heard that 4th gear will easily get you to 170 mph, and at those speeds the car feels hunkered down (thank you Camilo, and wind-tunnel testing) and quite stable/confident. There's also a low-frequency "thrum" as the air slams through the front opening, up through the hood's twin air extractors and over the windshield. And, if you're really sensitive, you can ascertain a slightly lower ride height as a result of the downforce being created.
At least, that's what I've heard... :banana