This does not address Smitty's question, but for those who are considering adding independant LED directionals and 4-way flashers, I can recommend Logolights, which can be used in 6v or 12v vehicles.
The system is completely independant of other vehicle lighting and wiring so they are easy to add and remove; the LED directional lights fit nicely into the space between the upper and lower horizontal bumper bars; both directionals can be turned on for the appearance of 4-way flashers, and the small signal/indicator unit which easily mounts magnetically under the dash rail lights-up and beeps so you know they're on.
At $200 from Snyder's, the Logolights system is not cheap, but my car's electrical system was such a mess that I wanted to have totally independant directionals and wiring, and I am happy with them.