There is no single best used race car on the market, as race cars are usually purpose-built or modified to the specifications of a particular type of racing. However, racing variants of the Porsche 911, Ford Mustang and BMW 3-series are popular and competitive models in a variety of racing disciplines, including endurance and drag racing.
The Porsche 911 has a long history of racing success in both endurance and rally racing. In particular, the GT3 variant of the 911 is sold with an optional Clubsport package that makes the vehicle nearly competition-ready from the factory. The roll cage, safety harness and fire extinguisher included with the package take care of many of the safety requirements of most racing series, making this vehicle a good choice for most on-track racing needs.
Ford's Mustang has been used as a race car since the model was first put into production. Ford has produced several race-ready Mustang models, including the Boss 302S model intended for on-track racing and the Cobra Jet Mustang intended for the drag strip. The wide variety of used race-ready Mustangs produced over the model's lifetime means that there is a version suited for almost any racing discipline except rally racing, due to the Mustang's lack of four-wheel drive.