when my 50 styleline had an intermitment knock I pulled the pan to plastigage all the lower bearings, ( which checked fine) I found a small spring in the bottom of the pan. I had no idea where that came from till I rebuilt my fuel pump and found this same spring in the rebuild kit. It goes on the pump arm. the pump arm must have been flopping around at various rpms. after replacing the pump, no more knocks. never can tell what you'll find in there, besides sludge.
later, bill