Coil wiring stock 6 volt

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I am in the process of replacing my main wiring harness in my 48 f-1 and I am almost done. Today I got my distributor to coil wire and I am confused. I bought the harness from Sacramento vintage ford. In the wiring diagram it says to hook the ringed wire from the harness to the + side of the coil, this would mean that the distributor wire goes to the - side of the coil. After reading about 6 volt positive ground systems, this seems backwards. Is the diagram correct? Any help is appreciated.