The Pontiac GTO races in both Speed GT
AND Grand-Am GT. The Racer's Group runs the Grand-Am team and just got their first win at Watkins Glen this past weekend. TRG has a bunch of factory GM drivers doing the work. Stu Hayner isn't going very far with the car in Speed GT, however, even though it looks really good and he's an above average driver with years of experience in cars from showroom stock to Trans-Am.
No Pontiac G6's listed on the season entry list for Speed Touring series (I doubt a privateer would show up at the last minute with one):
http://www.world-challenge.com/2005/entrylist-tc.html
Thread hijack over.