[Russell Ashley]

I thought something looked different about the image you posted but had to look at it a while to realize what it is. It is a mirror image and makes the bolt hole and lock plate appear to be on the wrong side. This is a correct view.
On my 57 3100 there is no step on the pin, it's just a tight fit. It's not much trouble to do it like Wrenchbender suggested and take the pedal arm out with the master cylinder. I did mine that way but I wanted to paint the arm anyway. I used a ball joint puller instead of the 2X4 method to remove the pedal shaft from the arm but either way works. If you really don't want to do it that way you might try to get a wrench on the flats and rotate the pin to loosen it up.