Successfully complete the indicated task to unlock the corresponding car:

Assassin Super Car: Get 150 Takedowns.
Custom Super Car: Win the Gold medal at the Dockside Race.
Dominator Super Car: Get 80,000 Burnout Points.
DX Super: Win the Gold medal at the Silver Lake Eliminator.
Legend Hot-Rod: Win the Gold medal at the Dockside Legend Face-Off.
Legend Special: Win seventy Gold medals.
Legend Super Car: Win the Gold medal at the Harbor Town Legend Face-Off.
Modified Super: Win the Gold medal at the Golden City Raod Rage.
Super Cop: Win the Gold medal at the Riviera or Big Surf Pursuit.