My kids and I have been building a 3-wheel car from the ground up. We have built the body out of urethane boards purchased from a local lumber yard. Glued the panels together with the spray urethane foam (Home Depot) and then covered both sides of the body with 2 layers of fiberglass and polyester resin. It is quite a job but a lot of fun for sure! Here are some pictures over the years...
http://picasaweb.google.com/stinger3wheel/Stinger