I like it. Two critiques (personal opinions):
1) The flintstone wheels kinda get to me (squared off selections?)
2) The extreme contrast of the black bg makes the colors look flat and also too unrealistic because the car does not reflect what should be reflected. (make sense?

This probably wouldn't have been a problem, had you taken the photo in the studio... so nice work for what you had. Maybe airbrushing a little more shadow along the underside might work. Not sure though.