The kickdown switch must momentarily short out the ignition to unload the drivetrain and allow the OD to disengage. It sounds like your kickdown switch isn't wired to do that. One of the wires from the kickdown switch needs to connect to the the distributor side of the coil, and I believe the circuit also goes through one of the contacts of the OD relay to prevent the ignition from staying shorted out more than a very brief period of time.
Jerry

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