Make an account for 2008 or 09 or whatever and say you make the birth date on December 23. Sign in on that day, send the car over to your main account, then delete the saved file on the fake account, make a new game and get another new car. I think the whole 'only able to send one car a day' thing still remembers that you sent one earlier so you would need to wait until midnight to send that car, so only 2 cars a birthday. If you don't like the car they gave you delete and make a new game until you find one you like.