Glennm27,
Great pictures!!! It allows to have a better idea of the dimensions for those of us that have not been able to see it in person yet
Is your Z06 lowered at all or is it on stock suspension and same tire profile?
YllsStgr,
I think that usually for optional larger wheels, they tend to go lower on the tire profile. This helps achieving accurate speed readings on your dash. So, in short, the circumference of the 18/19 wheels should be pretty close to the one of a 19/20 setup. That's just my guess though from what I have seen with other car models prior (not Corvette thought. I am Corvette virgin still

)
But I find similar information in the specs sheet:
Michelin® Pilot® Super Sport12 run flat, summer-only
front: P245/
40R18 (w/o Z51)
rear: P285/
35R19 (w/o Z51)
front: P245/
35R19 (with Z51)
rear: P285/
30R20 (with Z51)
The numbers in bold are the profile (wall thickness in milimeters) of the tire. So, the additional height (in centimeters) that is added to the wheel. So, from the center of the wheel should be:
On a 19 inch wheel rear you will have:
19 inches divided by 2: 9.5 inches
3.5 cm (wall profile) = 1.38 inches
total distance from center cap to ground = 10.88 inches
On a 20 wheel rear you will have:
20 inches divided by 2: 10 inches
3.0 cm (wall profile) = 1.18 inches
total distance from center cap to ground = 11.18 inches
So, it will sit 0.3 inches higher in comparison to the 19 inch wheel. If you get the specs of the Z06, you could calculate and compare it against the C7. I may be wrong, but that's what I came up with. Clearance on these cars are definitely a concern. My rules are:
1) Park on reverse
2) Hit the speed bumps diagonally
This should help some...