1968 LA Times Gran Prix at Riverside had a Road Runner as a pace car, it was also used to pace the Stardust Grand Prix Can Am races in late 1968.

this was a promo Road Runner that an LA Times illustrator was given to drive around to drum up interest in the race by free publicity.

Frank Bursinger, the illustrator for the Los Angeles Times that created automotive art for articles was  allowed by Chrysler to bring home the pace car for the Grand Prix, where he took the only known color photographs of the Road Runner.

The Omaha Orange Road Runner pace car appears to have continued on with its pacing duties, as an identical car led the field to start the Stardust Grand Prix in Las Vegas two weeks later.  These are the only known documented appearances of this car.

https://www.facebook.com/groups/429104630593174/permalink/518544744982495/

A 1969 Road Runner convertible was the gift to the winner of the 1968 Times Grand Prix, but race winner Bruce McLaren declined the car for cash instead.

https://www.hotrod.com/articles/help-us-find-omaha-orange-1969-plymouth-road-runner-1968-los-angeles-times-grand-prix-pace-car/