Have done the extra brake lights mod on my w126 using the high watters on a normal two element tail light/flasher bulb.
Puts out some SERIOUS light to the back of the car...I just went to take some pictures...






Inbalance there on tail lights...I have a few really old bulbs that need to be replaced

EDIT: My licecene plate lights aren't working again...damn them...I need some dialectric grease