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In the stock setup the switch on the shifter sends a signal to the ECM which then powers the O/d relay on the firewall because the ECM has control over O/d operation.If you run a wire to the relay( or in your case a new one) from a switch you then have complete manual operation.
I think this guy is talking about using the old style ON/OFF switch in place of the momentary contact switch in the shifter he has now and pulling the ECM wires at pins C8 and A7 and connecting them together.