[Nononsensecapeesh]

Originally Posted by Gerard C

If you follow the official name, those are sedans 2 or 4 doors homologated with room for 4 people, modified or heavily modified to adapt them to track use. Jags, Ford Mustang, Comet, Escort or Sierra RS, Rovers, Opels or Vauxhalls, Mercedes, Bimmers and so on. Assuming your question was a genuine one.
Those categories was a good opportunity for car makers to promote their road going models. Which had few to do with the racing models but their external appearance.
When chunderer says G1, he means Group1, car looking like a "normal" car.

Back on subject, Stewart Lines, bless him.