Low Oil Pressure and clanking noise

Several possibilities that come to mind that I can throw out.

1) Worn out engine - rebuild time.

2) Oil return holes in head stopped up (under valve cover) oil goes to the top, slowly goes back to the pan - unstop holes.

3) Oil pump shot - replace.

4) Oil pump pick-up screen stopped up - clean.

Maybe the first thing to do is to remove the oil sender, install temporary mechanical oil pressure gauge. You can make one like mine (picture below), or buy an under dash mount unit (do not mount it). Run it out from under the hood and into the cockpit. This will give you a "real" pressure reading to compare to what you already have. This might affirm your pressure is fine and maybe your sender or dash gauge is bad.

The racket you discussed may be permanent damage or on the way to it. Could just be starving for oil. Maybe "2", "3", or "4" could be possibly ease your pain.

Keep us posted.

The Medic

No, the pressure increases at higher engine speeds which proves the pump is capable of developing the needed pressure. It is not capable of delivering the needed volume at low speeds, and that is usually due to worn engine bearings. The oil runs out of them too easily. Your mechanic can check the actual oil pressure with a mechanical gauge, and if it is okay, the sending unit is suspect. Given the additional symptom of internal engine noise, the bearings are the better suspect.