one of the few car models I've wanted to see in person, but have never found at a museum, car show, cruise or on the street while out walking around or driving around, the Buick Century Free Spirit, which had two sticker appearances

https://www.hagerty.com/marketplace/classified/1975-Buick-Century/3ccdb082-ab1e-4318-92b6-4f741e25bae2

https://www.virtualparking.net/post/702/1976-buick-free-spirit-official-pace-car

https://www.junkyardlife.com/2012/08/cars-in-yards-1976-buick-century-free.html

Seems that Parnelli drove it up Pikes Peak! 

https://www.pinterest.com/pin/325807354304899686/

https://justacarguy.blogspot.com/2017/04/1981-buick-regal-was-pace-car-for-indy.html