Your oil pressure gauge is mechanical and has an oil line running to the back of it. It either is leaking at the fitting or the line has cracked. You can get new plastic line to run from the engine into the gauge or replace it with another flexible metal line.

 

how do you disconnect the line can't get behind the dash to see and my right hand is broke can't rely on left to feel

 

You could disconnect the line at the back of the engine and just put in a gauge at this location. You would need to either go from under the dash or pull the cluster to get at the line at the back of the cluster. I wish I had taken some pictures when I refurb'd my dash in my 74.