Ford has frequently changed the model used in NASCAR over the years, going from the Thunderbird to the Taurus to the Fusion. Chevy, meanwhile, stuck with the Monte Carlo for years until the manufacturer discontinued the model entirely, causing them to switch to the Impala.
For many years, Hendrick Motorsports has been the standard bearer for Chevy cars in NASCAR, with its cars driven by the likes of Jeff Gordon, Jimmie Johnson, Terry Labonte, Mark Martin and Dale Earnhardt Jr. Roush Racing has been the leader for Fords, with its drivers including Kurt Busch, Carl Edwards and Greg Biffle.
Chevy has won 27 manufacturers' championships in NASCAR, the most of any brand. These are among the 31 total championships that General Motors has won in NASCAR. The Ford nameplate has won 12 of the 13 championships held by the Ford Motor Company.
Both manufacturers' contributions to the cars themselves are simply the parts and design for the engines. The bodies of the cars are actually regulated by NASCAR, making the exact shape of each car identical--especially since the inception of the "Car of Tomorrow." The cars are painted to resemble the appearance of their manufacturer's brand, but that is more cosmetic than anything.
Chevy motors have become known for the best horsepower and performance, particularly with the Hendrick engines; many other teams actually buy their engines from Hendrick. Fords, meanwhile, are best known for their fuel mileage
While many NASCAR drivers show support for the brand their team uses, those who drive Chevys show a particular loyalty. Dale Earnhardt Jr. chose Hendrick over Joe Gibbs racing, and Tony Stewart left Gibbs to form his own team, because of Gibbs' decision to switch from Chevy to Toyota.