1972 dodge dart with oil light flicking

My 72 dodge dart has a slant 6 225 engine. The oil light flickers at low RPM but remains steady when I operate at normal road speeds. The oil and filter were just changed without any change in the flicking of the light.
This car has around 160k on the original engine.his
I checked the PVC and it is working fine.
What could be causing this oil light to flicker?