The "R" was for secondary Ignition, to provide continuous power to the coil resistor during cranking cycles.
Check to see if you have power when you try to start in "Start position" at the coil..If you do...no sweat..just abandon the wire..
If you don't, you can create a secondary Ignition by using a relay, hook the coil power to the "S" terminal, and ground, the NO (normally open contact) should go to a fused 12 volt direct supply , such as the Battery or big bolt on the starter..The Cw (Center wiper) should go to the wire you now have..This will provide uninterrupted power during crank, when the rest of the car goes dead.....
Does the car start and run now? no problems? If so just abandon the wire..you should be fine.