To unlock the Steel Wheels car, head to the in-game cheats menu, where you can insert "Sponsor Codes". Insert the following password to unlock the car: U84D 3Y8K FY8Y 58N6.

When you have acquired the Level A license you can insert these following cheats to unlock sponsored cars. Type them in the sponsor codes section. Or at the in-game cheats menu. I think they are the same thing. Best Buy Car - BESTBUY Circuit City Car - CIRCUITCITY Gamestop Car - GAMESTOP Wal-Mart Car – WALMART