Well you should start at the top! Look at the OEM bulb and connections, notice how many there is and how they make contact, and which do what, take your multimeter and test the voltages coming out with the bulb off, with your headlights on, and with your blinkers on... find out how your car blinks the lights, does it have a older tin can style or black box style blinker/flasher circuit that plugs into your fuse or relay box??
I'm assuming the car has 2-4 wires, 1-2 for the constant bulb that's on when you turn on your headlights, and 1-2 for the blinker bulb. (I'm saying 1-2 because it depends on if the lights are chassis grounded)
If i'm on the right path, you should just have a continous 12v terminal and a "blinker" 12v terminal that would "flash" 12v as the blinker relay clicks... Then all you should have to do if wire up 2 seperate light ckts, for example if it's 12v, and you get some ~3v leds than you could just wire up 4 in series to the constant terminal, and another 4 in series to the blinking terminal.
FYI that's just a quick dirty solution. If you really want it to look nice and last, maybe get 2 12v piranha light bars and use a simple filter/rectifying/smoothing circuit to clean up the noisy DC of a car. (12v piranha light bar is a ready made string of super bright leds wired for 12v operation.. they run like 8-15$ a piece, check out besthongkong.com for all kinds of cheap 12v auto stuff)
*P.S., I've run leds off the car power with no problem, but that was years ago as a teenager, I'd really reccomend getting some advice on how to simply and cheaply clean up the DC. Even a 1$ cap to the chassis or something may help alot. Don't quote me on that :whistle:
