Continue to troubleshoot or start from scratch?

Hi again, been crawling around the car for the last few nights tracing wires, cleaning terminals, etc. I unbundled the neutral safety switch harness from the headlight harness and fished it down to the transmission. Jacked up the car and crawled under. Having never hooked up a neutral safety switch before, I assume I'm looking at the right place, right below the shift lever. What I found there won't connect to the 3 prong plug I fished down from above. Any ideas what this is? It's a threaded stud with a nut on it.
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