Group 6 was the official designation applied by the FIA to two motor racing classifications, the Prototype-Sports Car category from 1966 to 1971 and the Two-Seater Racing Cars class from 1976 to 1982.
Porsche won the 1969 International Championship for Makes with the Group 6 Porsche 908
Porsche won the 1976 World Sportscar Championship with the Group 6 Porsche 936. The type also won the Le Mans 24 Hour in 1976, '77 & '81 and was runner up in '78 & '80
Group 4 referred to regulations for sportscars and grand touring (GT) cars used in racing and rallying, as regulated by the FIA. The group was introduced in 1954 and was replaced by Group B for the 1982 season.
A Ford GT40 contesting the Group 4 Sports Car category at the 1969 1000 km Nürburgring
A Group 4 Porsche 906
A Group 4 Alpine A110 1800
A Group 4 De Tomaso Pantera GTS