Get first place in the indicated race in the Amateur Race Series to unlock the corresponding car:

#22 3R-Racing Viper Competition Coupe: 5X5 V10 Super Sprint
1973 Porsche 911 Carrera RS: Sports Car Classic
1992 Toyota Do-Luck Supra: Boosted Shootout
2000 Acura VIS Racing Integra Type-R: Inline 4 Showcase
2002 Chevrolet Lingenfelter 427 Corvette: Big Block Shootout
2002 Nissan Tommy Kaira Skyline GT-R R34: 6-Cylinder Showoff
Corvette Goldstrand Edition: American Iron Runoff
ME Four-Twelve Concept: Extreme Performance Shoot-Out
Mugen S2000: Free-Breathing Challenge
VeilSide Supra Fortune 99: 20th Century Supercar Invitational