What's the most "stacked" slate of nominees in a category of all time?

I was watching Bonnie and Clyde this morning, as one does, and wanted to remember who beat Warren Beatty out for Best Actor in 1967. Googled it to see this slate:

Warren Beatty, Bonnie and Clyde

Dustin Hoffman, The Graduate

Paul Newman, Cool Hand Luke

Rod Stieger, In the Heat of the Night (winner)

Spencer Tracy, Guess Who's Coming to Dinner

Every single one of those is an iconic performance, even almost 60 years later (arguably, the winner is the least iconic).

So what other single year nominee slates look like this?