The Nominees of 1969 Best Picture was "Anne Of the Thousand Days", "Midnight Cowboy", "Butch Cassidy...", "Z" and "Hello, Dolly!" But What if there were 5 more nominees.
The One easiest to say would get a nomination would've been "They Shoot Horses, Don't They". It earned 9 nominations, one of them a director nod. Also another director nominee "Alice's Restaurant" would probably also been a nominee. Three more slots to fill. "Easy Rider" whom had 2 nominations for Screenplay and supporting actor was the a both critical and commercial success
Musicals like "Sweet Charity" and "Goodbye, Mr. Chips" would probably not be on the top 10 cause of the Musical slot already taken by "Hello, Dolly!".
Then the other two. There are three contenders:
"Bob & Carol & Ted & Alice" a commercial success and 4 oscar nods, but it didn't earn any GG nomination for comedy so I doubt it's position.
"True Grit" John Wayne's popular movie, is a contender but maybe it would be one western too much.
"Oh What a Lovely War" It didn't earn any Oscar nods, but It got a DGA nod.
Of these three I choose "Oh, What a Lovely War" and "True Grit".
Anne of the Thousand Days
Butch Cassidy and the Sundance Kid
Oh, What a Lovely War
They Shoot Horses Don't They
The Nowaday classic "Once Upon a Time in West" would certainly be nominated in retrospective. But at the time it wasn't that big success.