Brake/clutch pedal question

When I convert my Dart from a 4-speed to an automatic, I'd like to take out the 4-speed clutch/brake pedals and put in the full size brake pedal from an automatic car. What I would like to know is, will I have to swap out the entire bracket that the pedal swings from or will I be able to just remove the 4-speed pedal arms and install the transplant automatic pedal in the same bracket? I don't have any knowledge of whether automatics and 4-speeds used the same bracket that the pedals hang from.