Yes FID, that's the one.
I thought I should be able to get the whole master cylinder out as well, but the pin attaches the brake pedal and the brake pedal goes through the floor board. It's a shame it isn't seized on the pedal instead of the push rod. If it was frozen to the pedal I could get it out.
In your pictures, the brake pedal is to the left side of the first 2 red circles you drew. It's misleading since the brake pedal has an offset in it.
As you can see, the pin goes right through it. The pin has to be driven toward the frame and there is just no room. If I can't find the original bolt, I think I can use a tempered bolt with threads and double nut it. There can't be much pressure side to side since the pin only has a cotter key to retain it.
I think I can get the old pin out by cutting the head off with a Dremel cut off wheel.
Thanks for your input!