After a successful 1966 season privately campaigning a Shelby GT-350, Mark Waco was able to secure sponsorship from renowned Indy car owner Bob Estes to compete in SCCA racing.

The Bob Estes 1967 Cougar XR7 racked up 6 wins in 10 races in the 1967 season and 6 of 17 races in 1968. Famously, the Mercury Cougar was running in 4th place at the 1968 Mission Bell 250 Trans Am race at Riverside, CA before a broken brake rotor put the car all the way back to 15th place.