The #12 given to Joe Namath ("CC") for the Moto X Race is the same number he wore on his jersey with the NY Jets.
Inside joke: Name of Sue Mengers, future 1970s super talent agent, appears as a supporting act on a motel nightclub's marquee, right below "Wayne Cochran and the C.C. Ryders". In real life, Mengers was Ann-Margret's agent.
The biker gang name "Heads" is a reference to drug use, such as "drug-head", "hop-head". It was a common term in the late sixties / early seventies. In many high schools it was commonly used as a reference to the long-haired clique (as in "straights", "socials", "jocks" and "heads".)
Writer Roger Smith and actress Ann-Margret were husband and wife. (8 May 1967 - 4 June 2017) (his death).
There are several edited versions of this movie. A television broadcast version, PG Rated version and the theatrical R Rated version. Streaming online, Amazon Prime Video has the PG Rated version. (Complete with continuous intermittent 'Digital Audio Dropouts' and several minutes of 'Black and Silence' after the end of the movie). The Internet Archive appears to have a R Rated version, but again that too may be slightly edited.
According to a contemporary Tuscon newspaper article this is the first film in which Ann-Margret did a nude scene.
Actors Bruce Glover (Captain Midnight) and Sid Haig (Crow), who play bikers, would later play bad guys in the James Bond film, Diamonds Are Forever (1971), the following year.
Wes Stern, appearing in ABC's Getting Together sitcom with Bobby Sherman, at this time, appears as the first hitchhiker driver in the first 15 minutes of the film.