The Boss 429 exists because NASCAR’s rules required Ford to produce 500 road cars equipped with the 429 cubic inch engine it wanted to run at Daytona and Talladega. The engine — designed specifically for high-speed oval racing with a semi-hemispherical combustion chamber configuration that Ford called the Crescent chamber — needed a Mustang body around it to satisfy the homologation requirement. Ford called Kar Kraft, a Michigan-based specialty builder, and Kar Kraft cut the front shock towers of the standard Mustang body to fit the wide engine, moved the battery to the trunk, revised the front suspension geometry, and delivered approximately 859 cars in the 1969 model year and 499 in 1970.

The Dodge Charger Daytona is one of the more extreme objects ever to wear a manufacturer’s badge and a license plate simultaneously. The 18-inch aluminum nose cone that replaced the standard Charger’s front end was designed in a wind tunnel at the Lockheed facility in Burbank. The 23-inch rear wing — positioned high enough that the trunk lid could still open — was there not for aesthetics but because the aerodynamics of the standard Charger body at 200 miles per hour produced lift that made the car dangerously unstable. Chrysler’s engineers needed the downforce. They also needed to sell 500 examples to homologate the car for NASCAR. They built 503.