I had to put ballast resistors on mine when I put LEDs in back. I put them on the Flasher Relay terminals 3 & 7 to ground. As for changing the flasher, see if the old one works. I ended up changing mine to an electronic one, but not the one usually sold, because I didn't change the front lights. The fronts are light enough and they look better if the color temperature is the same as the headlights.