If a ground wire is added (good idea, BTW) use a piece of high-flex wire such as what is used on multimeter test leads. The constant flexing caused by the motion of the vacuum advance will metal-fatigue the wire strands and cause them to break inside the insulation. That's also a good idea for the wire from the coil (-) terminal to the distributor.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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