In factory configuration there was a harness fastened to the front of the lower pan and the plug where the boat side harness connects is where your kill button is now. You can drill the lower pan or remove your kill button and run the wires out there. I have a ’67 that was either converted or missing the motor side harness when i bought it. I put a start button and a lanyard kill switch on the port side of the lower pan and ran the battery cables out the fron where the kill button would be.
-Ben