Answer:
Its not an answer, just an advice, find dealers who specialize in either selling custom parts for trucks and cars or find shops which customize whole trucks and cars. They would be willing to be a part of the show and will obviously be interested in sponsoring the event. You have to, though, assure the 'potential sponsor' that many people, who are genuinely interested in customized cars and trucks, would turn up. You have to first conduct a survey of people who would potentially be interested in such an event and then approach the sponsors. Once you convince them, you've a show to organize!!