Obviously not the best of sources but both the Penn Central Post (9/70) and Daughen and Binzen's The Wreck of the Penn Central indicate that Moore was selected by the trustees, with a approval of the bankruptcy judge. Unfortunately neither source elaborates on the selection committee, selection criteria, etc.
The PC Post reported:
On August 12 , the trustees announced their selection of a new president and chief executive officer:
William H. Moore, executive vice president for operations of the Southern Railway System. With Judge Fullam's approval, Mr. Moore assumed his new position at Penn Central on September 1.
In announcing his appointment, the four trustees stated:
"Mr. Moore's selection is the essential first step to get the Penn Central back into effective operation.
"He is thoroughly experienced, tough-minded, get-it-done executive. He knows how to run a railroad, and has been doing it successfully for 25 years--as trainmaster, division superintendent, general manager, vice president in charge of operations, and most recently as executive vice president for operations of the Southern Railway System.
"Mr. Moore will be given full responsibility for turning this situation around, and right now. His record makes him one of the best qualified men in the business to do this.
"With Mr. Moore's selection, Penn Central is on its way again."
Blah, blah, blah.
I'm only guessing but I would imagine Moore's being with the well-respected Southern had a major bearing on his appointment at PC.