The more I think about this idea the more I like it. I think the story is that a group of convicts overpowered a guard and stole his car just to take it racing at 24 Hours of Lemons.
We paint the car up to look like a pretty legit cop car. We stencil WASCO STATE PRISON on the doors and stencil the numbers on the car as well. A decent looking light bar can be made from cardboard and paint. It won't last on the track, but I don't think we want it when we're out there anyway. Then we just rattle-can graffiti, slurs, and other hate onto the car so it looks like the convicts did it on their way to the race. The convicts can bribe with a cake with a file in it and threaten the judges with home-made shives. In the back of the car is a bound and gagged prison guard. There is also the option of pouring cheap wine into a trash bag and using it as a bribe claiming that it is pruno. If you guys want to you can up your prison cred by using sharpies to give each other "prison tats" on your forearms, necks and faces.
On the back of the car we can tag stuff like, "Pass and you'll get shanked", "You're my bottom bitch now", "My other ride is your mom". Elsewhere on the car can be "Fuck da Police", "Snitches get stitches", "Die pigs die", "I ain't going back", "Murder for hire" and other things like that.
Also Alan, that link you posted if for a light that runs on 115V. Try this one.
http://www.amazon.com/Intensity-Volunteer-Firefighter-Emergency-Magnetic/dp/B00H4N3DX2/ref=sr_1_18?s=automotive&ie=UTF8&qid=1399994529&sr=1-18&keywords=police+beacon+light+12v