Compare yours to the pictures....
On the pin style, there is a shaft welded to the clutch pedal. That shaft rides on bushings in the pedal/steering column support. The shaft rotates when clutch pedal moves. The brake pedal merely rides on that shaft.
I'm not familiar with the bolt style, but I'll guess the bolt is secured in the pedal support and does not move, rotate, or swivel.
Each pedal has bushings that ride on the stationary bolt.
Guessing again, but I don't think the bolt style will work on a Buick pedal support.