We need NASCAR FAN to chime in here.......Rex White started the '63 season at Daytona with the '63 Chevrolet then switched to Mercury shortly thereafter. He also had another '63 Impala that started life as a 327, that car was street driven to somewhere out west, maybe Bonneville or the GM proving grounds. It was then converted to a race car and they ran speed trials with it. I've seen photos of the car, it was a red Impala with no lettering but had the mystery motor and racing supension.