It might be a knock sensor if its a blind hole, most all the big blocks I've had the oil sending unit plug was right above the oil filter near the back of the block which is whereve always plumbed my oil gauge.
Oh and I'd put a 150 nitrous plate on it : ) best bang for your buck and when you didnt want all that power you could just putt around on those puny quadrajet primaries.
Zoom Zoom. Charles