Are you just going for looks, or performance?
The OE brakes on the P5 are fantastic...it's got a lot of stopping power. If I was using this as a track car, all I'd do is upgrade the pads, lines and fluid to something a little more suited for track use.
If you're going for looks, then I'm not sure. I'm not a big cosmetic guy, as evidenced by my dents, door dings and oxidation.