My oil pressure gauge just quit on me. It now points straight up, way off the scale, 100% of the time. Even when I turn the car on it doesn't move. I was reading through the archives and it sounds like it might be the sending unit. But since it never moves at all, could it be something in the actual gauge? Thanks guys. (Its the 60 psi gauge if that helps at all)

 

I had the same problem with my Temperature gauge reading zero all the time and my oil pressure reading very high past the redline..... To make the long story short, i trace the my problems back to wiring...... 3 out of the 4 wires were cut. 2 of them belong to the temperature guage and the third wire belonged to the oil guage.
The wires of the temperature guage and the wire of the oil guage are spliced back together and everything is working like normal once again!
So try looking at the wires....
I have an 89 TPI and these wires are located near the firewall and the driver's side of the exhaust manifolds.... Good luck!