I HAVE A 71 BARRACUDA AND THE ENGINE HARNESS FRIED, I TOOK OUT THE OLD HARNESS,BUT WHEN I WENT TO ORDER THE NEW ONE COULD NOT DECIDE BETWEEN THE REGULAR HARNESS OR THE ONE MODIFIED FOR ELECTRONIC IGNITION. I HAVE MSD IGNITION BUT SEEMS INDEPENDENT OF HARNESS, WHAT EXACTLY IS THE DIFFERENCE BETWEEN THE TWO HARNESSES