If the needle is point straight up when the engine is running you have 45 pounds of oil pressure as delivered by the oil pump to pressure feed all frictional surfaces.
For a Chevy, you have very good oil pressure if you are using the recommended 5W-30 oil. The needle may drop off somewhat as the motor idles. As long as you have 25 PSI at idle your bearings are in good shape and the oil pump is working normally