Thanks for everyone's input. Going to have to research 19's to see if they will cause any difference in handling or cause any problems with the suspension before I make a decision.

I also own an '03 Z06 and changed wheel size on it. Fronts are now 18x10 and rear 19x11.5 running PS2's. No problems with handling or suspension problems.

 

To me, the big question is how you intend to use the car. If it's primarily on the street, then 19s will be fine. If you intend to use it on the track quite a bit, then you should consider 18s.

 

In case anyone searches this topic in the future, for reference:

I'm running

Wheels : 19 X 8.5" (45mm) fronts / 19 X 11" rears (52mm)

Tires: 235/35/19 fronts and 275/30/19 rears

The lips of my rear wheels are flush with the exterior body part of the fender, if not maybe 1mm beyond it. Will need to roll the rear fenders if I start seriously driving it around.