Corvette Summer (1978)

Directed by Matthew Robbins. Free with ads on Youtube. Mark Hamill, Annie Potts. 

https://en.wikipedia.org/wiki/Corvette_Summer

https://www.tcm.com/tcmdb/title/647/corvette-summer#articles-reviews?articleId=97177

https://www.avclub.com/the-gumball-rally-corvette-summer-1798201078