Automatic brake pedal, is there a difference?

[sigshooter]

I recently ordered a complete power brake set up from a member and it came complete with the bracket under the dash and what was described as a rare automatic only brake pedal assy. I am not saying it was falsely advertised, I just cant see a difference between my 4 speed brake pedal and the automatic one. I of course removed the clutch pedal years ago when I changed over to an Auto trans but my brake pedal is the 4 speed one still.

What am I missing? I want to know before I go to the trouble to change it and there is no difference, or worse throw it away and there is a difference I am just not seeing.