Look for a small, typically one-wire electrical switch, often mounted directly to the block or sometimes on an adapter plate near the filter. It might be facing upwards, downwards, or even to the side. You'll likely need to get underneath the car or remove some components (like the air cleaner) for good visibility.
A shop manual specific to your 327's year will show the exact location. Online parts diagrams, if you can find one that matches your engine, will also be helpful. Remember to use caution when working under the hood or near hot engine components.
