[1] The rulebook mandated that all cars had to be American made, and 1937 or newer, with full stock fenders, running boards and bodies if equipped by the factory, but their bumpers and mufflers had to be removed.

Specifications for the Sportsman cars mirrored the Modified rules as to bodies and safety, but restricted the degree of engine modifications.

[3][5] By 1956 NASCAR had developed a plan to phase out the pre-war coupes and sedans in favor "Late Models", identified as American cars produced between 1949 and 1955.

[5][7] Earlier car models remained eligible for the Modified division, which evolved to eliminate front fenders.

Within a few years changes began with the carburetor, and by the mid-1980s the stock front chassis was replaced with a racing clip, for safety and availability.

The affordability and availability of sheet aluminum emboldened racers to switch to making their own bodies, as it was cheaper and faster.

[11] Significant items such as the rear end and the engine are positioned on the left, while suspensions are constructed with maximum adjustability in mind.

[15] Dirt late model chassis are custom built by manufacturers within standardized dimensions that apply across most classes.

[9] Almost every NASCAR Cup Series driver raced in the class while progressing their career, and many crew chiefs have also developed through this level.