Pretty sure Mopar grounded them all pretty much the same from the 50's and up. (Between the firewall and right rear of the head)
I just checked my 60 Dart. Not sure if this wire is original. Since I restored my car back in the 80's I don't recall if I replaced it or not but that is where it is. I didn't check the FSM to see if it is shown or not but if your car doesn't have one in that area, I would certainly install one.