Almost all of the top SCCA T1 drivers are using Carbotech pads. I raced on XP9 front, XP8 rear for my first few races, then moved up to X10 front, XP9 rear in 03 and XP11 front, XP10 rear at my last two races this year. Great pads, especially for the money and American company. And, they are ceramic so the dust doesn't hurt the wheels as Norm alludes to above.
As mentioned above, they are carried by forum vendor PYFC.com (yellow link saying Corvette Store near the bottom) - look under the For the Track link on their website.
I suggest you start on XP9 front, XP8 rear if you are using R compound tires and move up from there. If you are on street tires, you might want to start with XP8 front, Panther Plus rear (a combo I personally haven't used).