Not a lot you can do on a small block.
Try a heavier oil and perhaps put a aftermarket
oil pressure gauge on your car so you can see how bad it
actually is. You do not need a lot of oil pressure at idle but you
need some!
You didn't mention what type of gauge you have. If it's the factory electric gauge like the one I have on my rallye dash then you could have a bad oil pressure sending unit that's located near the distributor. I had a new Standard PS59 sending unit and the needle on the gauge would go to the bottom after my engine warmed up and the car came to a stop. I changed to a Standard PS59 T-series unit and the needle stays in the normal range all the time.
Or the OP could have and old standard volume pump that is worn out. They really didn't give us much of a story on the engine, so it comes down to us guessing.