Intermitant Oil Presure Gauge

Since the others don't work, this could easily be a bad instrument VR.

I agree with Red---

My old 67 had a NUMBER of problems, and is one reason I try to get you guys to think of the gauges as an end -- to -- end SYSTEM

Pull the cluster

Check the power from ignition to the cluster, make sure it is same as batter

Evidently you have a Rally cluster which means your voltage limiter is built INSIDE the fuel gauge. If you google around there are a number of ways to deal with this, but basically you need to disable the VR in the gauge, and attach an external one and wire that in.

Otherwise, bad wire connections, bad ground to the cluster, and don't forget that the oil and temp gauge go through the bulkhead connector -- yet another place for a poor connection

Don't discount that there may be bad connections right at the senders. The temp/ fuel are molded connectors, can be broken wire internally or corroded or work loose. "Work" them on/off the stud to "scrub" the connection and inspect for corrosion. Good idea to buy a small bottle of electrical "anti ox" available at any place that sells wiring products. Both Lowe's and Home Depot should have it.