I added fender mounted turn signals to my 69 Dart. It seems I remember seeing harnesses made to fit with your standard harness for this purpose, but can't find them now.
As far as I know its just a single wire that comes off the light harness. If your harness does not have it you can just tap off the turn signal lamp wire. I dont know if they had a different harness for A01 package cars or not. I have seen some harness's that did not have the pigtail for the fender lights.