Why are the Vipers racing in two different classes? The SRT cars are running in the GTLM (GT Lemans) and Ben Keating (Riley Motorsports) is running in the GTD (GT Daytona) class. I Know there is a SRT GTS-R and the Viper SRT GT3-R, but what is the difference in the cars? Looking forward to a Over all sweep like in the old days, when Viper took the win overall. This year with the combination of the two different divisions of racing (Grandam and ALMS) both together this year should mix things up quite a bit. Mixing the classes gives no-one a definite advantage. from what I understand everyone has had to make changes to their cars. Only a week or so. Should be quite a show.