Here's what I got back from Lokar:
"It is in our catalog wrong if you have the brakes with the hook you will use the CC clevis. If you have one with a hole in it you will use the WC clevis. Sorry for the confusion if you have any more question Let me know. There was a few years that needed the Pin and then GM went back to the hook type later."
So maybe the C3 Corvettes used the pin.