if you lost your oil pump drive then your distributor drive would most likely go too, was the engine hot/cold, did it used to rattle on the top end cold till the oil pressure got up? does not sound good if it was running and oil pressure did dop off completely, I would fit a new oil pressure switch, remove the spark plugs and wind it over the oil light should go out, if it does then put the plugs back and start it, Rick