[2] Generation 4 cars feature highly modified bodies with teams spending hours in the wind tunnel to gain aerodynamics.

[4] In 1992, the Gen 4 car arrived at the sport when steel bodies became primarily custom made instead of using stock pieces, and wind tunnels became a staple as teams worked to gain aerodynamics.

In 1998, Ford introduced the Taurus, which was the first four-door stock car model approved for NASCAR competition in the modern era.

As of 2022, the Gen 4 car is still legal in the ARCA Menards Series West and East (though Dodge body panels are illegal); Hailie Deegan scored her first NASCAR win at the Las Vegas Motor Speedway dirt track in a Gen 4 Toyota Camry in 2019.

The Car of Tomorrow, by contrast, featured a symmetrical body in order to curb aerodynamic development wars in an attempt to cut costs.