The Questor Grand Prix held at the Ontario circuit in California was a non-championship event that took place in March 1971 and which pitted Formula 1 cars against a field of US Formula 5000 machines.
Labeled as the "Battle of Two Worlds", the race saw Ferrari's Mario Andretti win on aggregate following two heats of 32 laps from Tyrrell's Jackie Sewart and McLaren's Denny Hulme.
During practice, Stewart was asked to run a few laps on board AJ Foyt's Agapiou Brothers-entered McLaren M10B and provide some feedback on the Chevy-powered mount.
Giving this some thought, this may have been the first and only time the great Scot drove an F5000 car and a McLaren at an official race meeting...
