Do you have a mechanical oil pressure gauge? If you do, Check the fitting at the back of the block, by the distributor, oil line might be cracked. Just realized you said magnum 360, I'm not sure were the oil sender unit is mounted on them.
I would check the oil filter also. I've partially filled a filter, lubed the gasket and installed a filter on my dart only to realize that the gasket had fallen off and was laying in the ground!
