I was here when that happened and you have no idea what you are implying. The issue wasn't just about manpower it was about cockpit workload and the need for another body.

The issue was resolved when, after several airlines had dropped the 3rd person in the guppy (and the DC-9 was being flown as a two pilot airplane), ALPA agreed to a study on the safety aspects of the third person in the more automated and simplified 737 cockpit of the day. The study agreed there was no reason for the additional person and that pilot was eliminated.

The really good news was the final decision was made in the early 80s and the airlines were already furloughing pilots due to a reduction of operations. It was a double whammy for those of us involved.