hello what should a oil pressure gauge read for a good engine

 

About 1 bar at idle and 2.8 bar at 2000 RPM, normal temperature. These are minimun values. The pressure relief valve will open at 4 bar, so you won't see over 4 bar at normal operating temperature.

 

haynes manual says:

Minimum oil pressure at 80°C (176°F):
At 750 rpm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0 bar (14.5 lbf/in2)
At 2000 rpm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 bar (40.6 lbf/in2)
Oil pressure warning lamp operates . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3 to 0.5 bar (4.3 to 7.2 lbf/in2)

 

Actually the Ford workshop manual says 1 bar at 900 rpm, aprox. idle. And it's also at 10w-30, so if you are using a higher viscosity like 50, it's should be a little higher.