The most important decision for buyers to make when purchasing a used GT40 is whether or not to purchase an original GT40 produced in the 1960s or a continuation vehicle or a replica produced in later years. Only around 130 original GT40s exist as of 2015, making these cars rare and expensive vehicles on the used market. High-quality used replica GT40 cars are nearly mechanically identical to the original vehicles and are more available and less expensive than original cars.
Ford produced the original GT40 cars in association with racing company Shelby American as its entries for the 24 Hours of Le Mans endurance races during the mid-1960s. In addition to racing models, some road-going GT40s were also built for racing homologation purposes until original GT40 production officially ended in 1969. Ford also produced a supercar in 2005 that bears many similarities to the original GT40, but that vehicle was named the Ford GT rather than GT40 due to licensing issues regarding the GT40 name that arose between Ford and the British firm Safire Engineering.
Many firms build kit car and replica versions of the GT40, but the quality of these replicas can vary widely depending on the manufacturer. Only replica maker Superformance is currently licensed to produce official "continuation" replicas by both Shelby American and Safire Engineering. Many enthusiasts and reviewers consider the Superformance GT40 replicas highly desirable used vehicles due to the quality of the reproduction, as well as the company's official licenses. Safire Engineering also produced official GT40 replicas during the 1980s that may be available on the used market.