http://www.youtube.com/watch?v=_X8-6h3Py4k&mode=related&search= Oh yee of little faith. Go to about 2:10 on the video and you'll see Valtah ripping around the ring......this is from the GT2's official intro at IAA Frankfurt.
It's something like 6min 55secs from a Radical SR8. I believe this is the quickest lap time by a "road car" http://www.youtube.com/watch?v=dfqrHY_JEcQ