No problems:
The grey/trace wire that went to #20 is the feed for the tach (on a rallye dash). If you don't have a grey wire on the inside of the car coming from #20, then I presume you don't have a stock tach. The Mopar electronic ignition has the wire going to the coil negative (black/yellow?) and that is needed for the new ignition system, but it isn't replacing the grey wire. They're just two unrelated wires going to the same place.