John,
To answer your question, yes, the track pack wheels are the same as the optional silver painted wheels on the NON-Track Pack cars. The only difference is the tires. The non track pack has the 245 nero P-zero all season tires and the Track Pack has the summer-only 255 (ultimate high perf) P-zero tires. And yes, the 18 inch wheels will clear the track pack brakes. The brakes on the track pack car are identical to the other GTs, just the brake pads are upgraded.
Keith