My first thought is that the gauge is inaccurate.I would get a mechanical test gauge and hook it with a short flex line at the port near the distributor.
Be aware that a gauge without a orifice in the line will not damp out the rapid fluctuations and rapid changes that don't allow smooth gauge reaction to normal pump pulses.
Probably your gauge is electrically controlled and the sending unit is usually the weak link--they are often unreliable and being electrical in nature are sensitive to voltage fluctuations of any cause.So we want to test with a mechanical gauge.
The normal SBC needs at least 10 PSI hot at idle but a new engine would probably be near 30 psi.I don't think over 60 PSI, hot, at speed is normal or desirable.Relief valve setting(max pressure) will be reached usually before 1500 RPM.
Excessive oil pressure wears the cam and pump drive abnormally and wastes horsepower.
I think the gauge defective. My 2 cents worth!
