Dr. Harris' futuristic-looking car was actually a production car, unmodified at the time of filming - a Bricklin SV-1. The Bricklin was built in Canada but intended for the U.S. market, featuring high performance and a number of innovative safety features. Fewer than 3,000 were produced during its short run from 1974-1976.
According to a recent book about Donald Cammell, Marlon Brando was attached to star.
About 20 minutes into the film, Dr. Harris watches television while eating a meal. The television audio is from the third chapter of part three of Joseph Conrad's suspenseful 1915 novel, Victory: An Island Tale. The novel's central character, Heyst, who has renounced the world due to his ascetic upbringing, falls in love with Lena. He takes her away to his isolated island to live alone together, but others intrude on his plans - somewhat foreshadowing developments in the film.