Typically in a car show like this, you'll have awards set up into classes with first second and third place for each class. Like, Stock, Mild Mods, and Wild Mods. First second and third place for each. Then have a Best of Show, and some other awards, like "highest mileage" or "longest distance traveled to the show"
It would be nice to have trophies or plaques for each winner. Whoever would be handling this could contact companies that make or sell parts for our cars to sponsor the awards.
Just some suggestions...