Fitzgerald was clear on the book: Gatsby has predilection for English luxury and he owned a Rolls-Royce. So, the car could have been a 1922 Silver Ghost (three first pictures on this post).
In 2013 film instead, we’ll find a really nice american car, a Duesenber Model J (no matter that was born 7 years after Gatsby fiction death). Of course, the race cars on the movie are with replica car, not 3M$ real ones 😉
Both are gorgeous cars that I like to share with u.