Been looking around for a low profile brake light to mount high or low in the rear window of my 49 GMC 1/2 ton. Best I've seen so far is a 1/4" by 6" strip of red bright LEDs for 6 or 12 volt systems that the Lereyn Co. sells (
www.thirdbrakelight.com). They install permanently or on a velcro strip for fast on-off, inside the glass or outside. And they don't take up much rear view.
Anybody try these or salvage a 3d brake light from a late model wreck?