The "Fireball 500" is a heavily customized 1966 Plymouth Barracuda, with a 273 V-8 engine.
Dave Owens' #43 Plymouth Satellite was actually Richard Petty's car for his abbreviated 1965 NASCAR season. Chrysler chose not to participate in the first half of the season, limiting Petty to 14 races. He won 4 races, finished all of them in the his races in the top 10, and ended the season 38th overall.
Although backgrounds of many scenes include posters for various car races, portions of all ads are masked by black tape, probably to disguise the fact that dates and/or locales of events didn't line up with when and where story was really taking place.
The blue moonshine car is a 1960 Dodge Dart, distinguished by its forward facing rear fins just ahead of the taillight bezels.
First of two racing-themed movies that features Fabian and Annette Funicello as love interests. The second is A Pista do Trovão (1967).
William Asher: in the Riverside Raceway scene near the start of the film; he is seen in the announcers' booth on the right wearing a dark green shirt and holding a clipboard.