Unlock these Mustangs by beating the time in Time Trial Mode:

1971 Mustang Boss 351 - Beat 3:10 in San Francisco Alternate Time Trial
1976 Mustang Cobra - Beat 3:05 in Chicago Standard Time Trial
1995 Mustang Cobra R - Beat 4:10 in Los Angeles Standard Time Trial
1999 Ford Racing FR500 - Beat 3:25 in Miami Standard Time Trial
Mustang 10L Boss 429 Concept - Beat 2:57 in New Orleans Standard Time Trial
Mustang 6.1L Cobra R Concept - Beat 2:10 in New York City Alternate Time Trial