Here is the GT2 C6R as it tested last week as seen on the ALMSF masthead.

As you can see from the photos, the hood window is gone, but the car does bear a resemblance to the ZR1 with a few minor tweaks for the track. There's a revised grille in front, a large spoiler out back and a new diffuers underneath, but other than that it looks fairly close to the stock unit. If the hood window remained you'd see a 6.0-liter LS7 this year, which will be replaced by a 500-hp, 5.5-liter race-tuned LS3 for 2010 when the rules change next year.

Source: Badboyvettes

What changes have been made to turn the R8 into a GT3?

Out goes the Quattro four-wheel drive system, prohibited by GT3 regulations. That means rear-wheel drive, with power sent through an all-new six-speed sequential 'box. No word from Ingolstadt on what engine powers the R8 though. We know it has over 500bhp, but is it a V8 or a V10? This car's R16 tag gives us no clues – it’s not a Bugatti Veyron engine.

Other tweaks and changes including junking the leather-lined interior, fitting a full roll cage and that enormous rear wing. Combined with the new front spoiler, side sills and rear diffuser it should create plenty of downforce. So even though the four-wheel drive system has gone and the suspension is apparently little changed over the production car, Dr Ullrich is claiming the R8 ‘is nevertheless easy to handle.’ We want one.

Source: CAR UK