I don't know why on earth you would want to do that. I BELIEVE you can get (such as Valley) towing converters that are a "black box" you hook up to change from one to the other
Otherwise you would have to figure out how to have separate bulb filaments for the stop lamps, and then simply disconnect the brake switch wire from the TS switch and extend it to the rear and then hook it up to your added stop lamps
You know, these, mounted up on top of the trunk 'er somewheres