Joe -
There was a good discussion with lots of ideas on this thread:
LED Lights
The "typical" LED bulbs seem to be dim, and because they don't draw as much current as regular bulbs, may require a special "variable load" signal flasher. The Halogen bulbs are brighter, but draw more current, and run hot - may require a wiring upgrade, and, in severe cases, may damage taillight lenses. Couple guys have found brighter bulbs from hot-rod wiring suppliers
Ron Francis that have brighter bulbs that do not burn as hot as Halogens.
I suggest you read all of that other thread, some other guys had some creative custom LED solutions.
regards,
Jeff