Car show lens for the 1DMKIV ?

Considering that you'll be relatively close to your subjects here, you're going to need to stop down to around f8 or more to get most of the car in focus. In which case you're f2.8 lenses would be money wasted. I'd be more likely considering the 17-40mm f4, or 24-105mm f4 IS. Just my thoughts.

-Paul.