Did you use a micrometer on the crank? Did you measure the gap on the new bearings with plastigauge? THe idle should be about 700-800 RPM, and your oil pressure should hold up at idle to at least 30 pounds when hot. Get a mechanical gauge and find out. You might be losing oil somewhere else... in the top end someplace?

A flickering light can mean a bad oil pressure sending unit.

I would pull that & either check pressure or just replace the sending unit if its cheap enough

before doing a motor.

If your going to even think about using the old pump , you tear it down & take clearance measurements, make sure it has no scratches on the cover & rotor, clean & check the valve & replace the spring that determines pressure.,.

Or just replace it with a new one.

You don't just slap the old one back in..

An oil pump in n engine , is the same as a heart in a person.

If either one is bad , neither one lasts to long

The oil pump pumps up the oil from the oil pan but the pressure is mostly created by the oil galleries and journal bearings.

It's like a water garden hose. You cover the hose opening with your finger to create pressure.

On old cars, their journal bearings have wore out so, oil flow through them more freely. Reason why they use thicker oil on older cars.

id warrant someone just slapped in bearings without bothering to see a machinist. you get what you pay for

try this gizmo