[JAJ]

First, if you haven't had significant problems with fade, then it sounds to me like you're on the wrong pads. The shaking is from pad deposits on the rotors. You say you've tried track oriented pads, but have you tried real racing pads like the Pagid RS19's or RS29's? If you're having shaking problems with those, then something else is wrong, like ball joints or something.

Second, as THE TECH said, you could probably gain some benefits from managing the brakes better. I've seen (and posted about) professional race drivers in my car on stock brakes and tires having no problem catching and passing heavily modified cars on a track that's notorious for brake problems. They just manage the brakes differently.

Third, if this is really about getting a BBK (as opposed to not getting one in my two points above), then the small Brembo 365mm kit or the Stoptech 355mm kit will fit under the factory 18's. The AP Racing kit will fit with a 10mm spacer. All of them will work well for you, and the Stoptech pads are excellent. I'm running them on my Mustang Brembo as street pads and they're very likeable.