UPDATE:

I fired it up and the oil pressure went to 38-40psi cold High Idle (which is normal on this gauge) and after about 10 minutes of fast idle, it worked its way downward. At an idle of 1200rpms, the oil pressure looks like 12-13psi which is also what I would call normal on this guage. It appears that I am back to what I would call normal oil psi readings for this car.

Issues:
The main issue that I found while swapping out the Holley fuel pump safety switch was that when I tightened down the three screws on top of the switch, they were tight. But what I found by mistake was that the screws were tight, but the wire ferrules were not! So I added a washer to two of the three screws and the wire ferrules are now tight.

I mentioned earlier that when I first noticed my oil pressure went down after that first drive after the oil change, I noticed when I got back to the garage that one of the three screws had come loose on the previous FPSS. So I tightened it up but there was no change in the oil pressure. When I swapped over to the new FPSS, that is when I found that the screws were not tightening down on the ferrules even though the screws were tight. I now have a backup FPSS

My fuel pressure is now back to normal too. One of the wires on the FPSS goes to the fuel pump.