No, 65/66's don't have brake warning lights. According to post #25 from the thread below (very knowledgeable Mustang guy) you can use the parking brake warning light for both (actually a 67/68 part), which is a great idea because I've left the parking brake on more than a time or two... wondering why the car feels sluggish...
http://forums.vintage-mustang.com/vi...-sensor-2.html