I would be willing to bet your wire to the sender is either not connected, or the insulation is chaffed and grounding out somewhere. My 88 has issues with the light because the wire has a short, every bump I hit makes the light turn off . The first time I had an issue with it, the wire had fallen off the sender. I did about the same thing as you, saw the light and left it parked till I could figure it out.
With the way our engines are, it is hard to have no oil pressure as long as you have oil in them.