oil pressure alarm.

Driving my 91 OCC tonight I came down the offramp and two things happened.

1. the steering wheel shook violently under braking (and also later when I hit a bump at 35 mph).

2. there was a fast chime and the oil light when on. I looked at the gauge and it showed 0 for the pressure. When the light turned green and I hit the gas it popped right back up to about 18.

I'm thinking the first is the crappy tires on it, the second, maybe an electrical failure in the dash?

I am thinking something in your suspension has broken perhaps a balljoint.When it broke a part of it flew up and struck some of the sensors on the drivers side of the block and oil pan.
JMHO
Jim Gordon

I had an LO3 loose oil pressure. I gave up trying to figure out what caused it, and put a used LO5 in it.

It would have 0 oil pressure at idle, and about 15 when driving. Sometimes 5 when driving. Check the oil pressure with a mechanical gauge. I think a/the bearings get loose, and won't hold the pressure. I even tried some heavier oil, to no avail. I think it cost me as much as a junk yard engine, trying to troubleshoot. It was a pain with the chime going off all of the time.

A friend of mine said he had an LO3 with no oil pressure like that, and it worked for about 2 years before it quit.

The braking issue is wierd. I had a spindle nut back off recently, and it caused some wierd issues. Check you spindle nuts. Check for other loose parts too.

happened again tonight. drove about 30 miles, came down the off ramp and while I was sitting at the light ding ding ding. worse part is the oil light hides behind the steering wheel so it took a second to figure it out.

Gauge said 0 pressure but the engine was running. As the light turned green it popped up to about a third on the gauge (had to drive so I couldn't read the numbers). Was fine after that....pretty weird.

It could be a sticky relief valve in the oil pump. The valve is a rod held in place by a spring. If it sticks open, it will vent pressure.