I agree with wbr. No matter what you decide to use make sure it uses compact flash or sd cards and a proprietary battery or secure battery holder. Vibration is a killer for in car cameras. If you have time to test look for one that is good in low light. The cheaper color cameras are terrible in night time race track lighting. I have built a couple of systems and always like to have the option to transmit live video to the infield as well. So be sure you can output to standard RCA while recording. The following incar link is put to music. It is several years old but still fun. This video I captured via a receiver in the infield.

http://www.brianone.com/documents/cody-072404.mov

The photo gallery also has some still photos of some different camera angles.

http://www.codyhansen.com/photos/photos.php