The answer to this question depends on what you would like to customize on your car. There are window tinting shops, shops that specialize in custom paint jobs, and even others that specialize in custom wheels or audio systems.
Some popular brands that specialize in creating high-quality wooden model cars include Amati, Ugears, and Wood Trick.
A great place to find repair shops is in the listings in your local yellow pages. They will make it clear in their ads that they specialize in classic cars.
There are custom body shops out there that do that kind of work but you could buy 6 good used convertible cars for what it would cost you to have yours custom made.
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!!
Car body shops are usually known as jack of all trades for vehicles. They are able to do small ding fix ups, or a full body repair. Also, some car body shops specialize in adding customized decals to cars.
Many parts stores can special order Lamborghini parts and have them shipped. Car repair shops that specialize in foreign cars can also get them in most cases.
Ebay is the best place for this kind of thing. Alternatively there are quite a few independent shops that specialize in them. Amazon is also a good Company to look at.
Typically, the productions rent old cars from prop houses in the area that specialize in old cars. They are stored in the individual company's warehouses. Studios do own some custom cars that they also keep in warehouses, usually off studio property.
the cars that have chromies are usally the realy nice cars or some other custom cars.
Wyotech would be the one to do it at. You'll get your best foundation at that school. I do believe there are custom shops not far from campus.
Coys of Kensington sells classic cars in the United Kingdom. They specialize in classic, exotic and racing cars. However, they have yet to establish a web presence.
Custom cars are usually advertised in newspapers or special periodicals devoted to customizing cars. I would suggest you start there in your search for a hot rod in the area.