In 1955, Jeffries custom painted Dean's Porsche 550 Spyder. Dean died in a wreck less than a month later.
Jeffries also painted many Indianapolis 500 cars.
For television, he created the Black Beauty for the 1960s show "The Green Hornet" and built the Monkeemobile in just 10 days. He also built movie vehicles, including a moon buggy for the James Bond film "Diamonds Are Forever." Jeffries also was a stunt driver and stunt producer on films such as "The Blues Brothers" and "The Fugitive."