Mark
The marker lights are hollow with red lenses. Their stems are too and the lamps are cemented to a square hole in the body. You may have to trim a bit of the window glazing to access the hole but it's no big deal. After that, all you need do is to insert the pico sized LED into the marker lamp. Affix it with tape, clay, rubber cement or Goo. Then hook the wires to your favorite power source. In this case, a 3V DC one. Since I didn't convert the rest of the interior lights, I opted for Evan Designs' universal LEDs for simplicity's sake. Like I said, it almost looks like Lionel had illumination in mind eventually.
Jerry
