The top GT class is contested by competition versions of such machinery as the Mercedes-Benz SLS AMG, Nissan GT-R, Audi R8, Porsche 911, Volvo S60 and Chevrolet Corvette. But last year it was the CTS-V that took top honors. Now back to defend its championship, the CTS-V has apparently undergone some aerodynamic upgrades, although Cadillac released little in the way of details. Reigning champ Johnny O’Connell will pilot one, with runner-up Andy Pilgrim driving the other. The new season kicks off on March 23 at the Honda Grand Prix of St. Petersburg.