Answer
The answer is a Chevrolet Silverado. Marco Andretti is a professional racing driver who competes in various racing series, including the NASCAR Craftsman Truck Series. He primarily drives the Chevrolet Silverado truck for the GMS Racing team, a well-known organization participating in the series. Andretti has achieved notable success driving the Silverado, demonstrating his skills and competitiveness in the NASCAR Craftsman Truck Series.