I HAVE A 71 BARRACUDA. I FRIED THE ENGINE HARNESS,WHEN I WENT TO ORDER THE NEW HARNESS , I COULD NOT DECIDE BETWEEN REGULAR HARNESS AND HARNESS MODIFIED FOR ELECTRONIC IGNITION I HAVE MSD IGNITION BUT SEEMS INDEPENDENT OF HARNESS . WHAT EXACTLY DO THEY CHANGE TO MODIFY THE HARNESS FOR ELECTRONIC IGNITION