This is from the second draft, dated September 24, 1973, which was a few months before production began.
Production actually began a few days later. FFC started filming with Anthony's party at Lake Tahoe on October 1. So the second draft is the final draft of the screenplay. They did however change some things during the production itself. A good example is Marlon Brando's sudden absense which forced FFC to rewrite that scene.
So this screenplay is in fact "officially" the final draft.
