According to the electrical diagram, there is a black wire with white stripe that runs directly from the ignition switch to the starter. This wire should be hot only when the key is in the start position, If it is hot in run also, then there is a problem with the switch or perhaps it is shorted to another wire somewhere that gets +12v during run. Old wiring is hard to figure the color code on but you need to verify the correct wire then trace back to the source of voltage.