Hey Vincent, You've named a lot of my faves from the 70s -- Picnic at Hanging Rock, Don't Look Now, the Philip Kaufman version of The Invasion of the Body Snatchers, The Wicker Man, Apocalypse Now, Deliverance-- whoa! Great list. You might want to take a look at my latest post on The Reincarnation of Peter Proud for more suggestions of 70s horror.

You left out some good ones (not horror, but great political thrillers): The Conversation (Coppola); The Parallax View (Pakula); The French Connection (Friedkin); Three Days of the Condor (Sidney Pollack).