You'll need a wiring diagram. Check how power gets from the ignition barrel to the starter and then to the odometer. (It's possible the odometer problem is a red herring). Check for continuity on those wires through the multi-connector between the ignition barrel and the main wiring harness. Again. I've seen individual terminals inside the multi-connector corrode and go bad. If so, you will need to run a jumper wire around the connector. Good luck and report back.