I purchased some red leds at a local automotive store for my rear turn signals. They, of course, flashed too rapid. But they are bright. I replaced the original flasher with a 552 flasher and now all signals operate normal. I had to cut the two wires they goes to the original flasher plug leaving about 4 inches on the original just in case I had to put it back on. Got two female terminals that fit onto the 552 terminals, heat shring on the terminals, and tied it with a tie strap right under the fuse box. I hooked the gray wire to the "L" terminal on the 552.
I also have the Kriss module that makes my rear turn signals wig-wag, flash, on all the time, etc. (The module has 12 different settings). All that works with the 552 flasher.
Hope this helps.