A 1969 Camaro RS/SS Z11 convertible was used as the pace car for the SCCA regional sports car event held at Laguna Seca Raceway in Monterey, California on Saturday, May 3, 1969. The event was one of the support races for the SCCA Continental Championship for Formula A/Formula 5000 cars that took place on Sunday, May 4, 1969. While I have yet to find any photographic evidence, the same Camaro was probably also used to pace the Continental Championship event.
This use of a Z11 occurred several weeks before the 1969 Indianapolis 500.
I found the picture on the Remembering the Original Laguna Seca Facebook page.