I thought the virtue of thermal pipes was the ability to connect a heatsource to a distant heatsink, such as in laptops. In this application, there's nothing stopping them from attaching the LEDs directly to the heatsink fins via a fairly modestly sized chunk of aluminum. (right?)
Interesting application though. Getting 50W of heat out of an auto headlight might be interesting, considering that the environment under a car's hood is already pretty warm. Maybe a better solution is to add a small radiator in front of the existing engine coolant radiator, and just use liquid cooling for the lights?