66 Dart Gt Idling issues/electrical

Ok everyone. New distributor is in. Vac advance to old distributor was bad. She is idling smoothly now. #1 plug wire was bad looked inside distributor cap and identifying Mark's are all identical. #1 had none. Is there a chance that I could be one spark plug off from the left to the right or voice versus. Because when I put the timing light on at 10° it wants to stall and backfire but if I put it 20 -30 she idles fine. Does anyone have a pic on your distributor? I'm about ready to move all wires back by one. I would upload a video but it wont let me. And yes I pulled the vac advance off to time