Looking at my 68 Factory Service Manual, chapter 5A for Delco-Moraine Power Brakes, there is an illustration of the Firebird brake pedal that shows this installed in the top hole of the brake pedal, with the pushrod clevis mounted in the lower hole.
I am converting my car over to a power disc brake setup from manual drums and I will be installing one of these clips on my pedal.
John
To err is human. To really foul things up takes a computer.