Sure sounds like a sender issue or the wire is gounding out. Pretty cheap to swap it and see.I have a 69 Camaro with a small block.
My oil light on the dash just came on driving to work today. I have an after market oil pressure guage and it is reading about 40.
Do I have a sender issue for the light?
I always have a mechanical gauge here at the shop to install temporarily and see what it says. Hopefully it agrees with the aftermarket gauge you have now.