Select the "Opponent Manager" option on the main menu. Click on the name of the car that you like, then go to the paint shop. Click on "Export" and enter a filename for the car decals. Go to the decals for the pit people, click "Export", and enter a different filename. Save, go to your car's paint shop, and click "Import". Find the filename entered for the car decals, click it, then select "OK". Then, go to the pit people and do the pit decals. Do a little work to change the number to your own and your car will have a customized appearance.