Not sure about the exact years it was used, but a resistance wire is easy to recognize. Because of the heat it develops, the insulation is a braided fiberglass material, usually tan or dark brown in color. The wire is stiff, and only has a few strands, silvery in color. The (+) terminal at the coil will have this type of wire, plus a normal copper primary wire that can be traced to the "I" terminal on the starter solenoid. If you unwrap the covering on the engine wiring harness, you'll find that the resistance wire is very long, and doubles back on itself to have enough length to drop the voltage to the coil sufficiently.

During normal engine running, the voltage at the coil primary should be about 20% below battery terminal voltage. For instance, a 14.5 volt charging system voltage will drop to around 9.5-10 volts at the coil (+) terminal.
Jerry


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