From Wikipedia:
“The series was best known for competition among American V8 sedans such as the Ford Mustang, Chevrolet Camaro, Plymouth Barracuda, Mercury Cougar, AMC Javelin, Pontiac Firebird, & Dodge Challenger in the 1960s and early 1970s. Marques such as Porsche, Alfa Romeo, Datsun, Mini-Cooper, Saab, and Volkswagen competed in the series Under 2.0 Liter category.”