First Corvette race car backed by GM (Raceway Enterprises, Doane Chevrolet) entered Sebring 12 hour race March 24, 1956.  Specially modified 377 cu in engine & 4-speed.  Drivers John Fitch & Walt Hansgen first in class of one.  (Ford Thunderbird DNS).  More details:  http://registryofcorvetteracecars.com/ee/index.php/site/view_cars/107