I think the Road King was getting jealous by all the mods going on with the Sportster so I bought it a new taillight. I had been running an aftermarket smoke laydown taillight with a Kuryakyn Iridium coated red incandescent bulb. The bulb has a silver coating so it didn't look weird with the smoke taillight. I liked the look but the thing I didn't like was that it wasn't very bright. I use a run/turn/brake module so the rear turn signals double as running and brake lights and since those are LED, they outshined the Kuryakyn bulb considerably. It was time for a change.
I bought a Custom Dynamics Genesis II smoke laydown taillight with 120 super bright LEDs.
Here's the old taillight (running light, brake not applied):
Installation was extremely easy. Remove 2 screws, unplug old light, clean housing, plug in new light, and reinstall the 2 screws.
Running light (brake not applied):
The pictures don't do it justice, especially in daylight. It's a lot brighter and more noticeable than the old light.