My 49-51 Mercury Repair Manual shows a Courtesy Lamp (Number 61) located on bottom (perhaps behind) lower left hand corner of dash right behind the dash board lights rheostat. It has its own mounting bracket. It has a black wire with a blue tracer and is tied in with the dome light. If you have a dome light check and see what color the wire is. Color of light is not mentioned, although RED light was thought to be "easiest" on your eyes.
There was an accessory emergency brake on warning lamp available. They are hard to find these days so folks pay a good price for one in good condition. It should have a switch in the E-brake mechanism to turn it on. It's generally mounted on the lower left side of the panel.