It is critical to your engine's life to know if the oil pump is working. The amount of oil flow is more important than the actual number on the gauge.
The main reason for the oil gauge is to indicate that the oil pump is working, even if somewhat. In my experience, the oil pressure with an original vane-type pump rarely goes above 12 pounds of pressure and might drop to 3-5 pounds when the engine is hot.
There should be a tube going from the top of the oil distributor (look between cylinders 2 and 3 on the driver's side) up to the gauge. Any oil pressure gauge can be hooked up to this tube, but the gauge should be a low pressure gauge, not one that goes up to 100.
All that being said, I'm sure that if you start a thread under the Parts Wanted forum for an oil pressure gauge, someone will have one laying around to sell you. You can also try Gary Wallace (
http://earlychevyparts.com/). He seems to have quite a stash of used parts.
Cheers, Dean
