spun cam bearing

I don't think so. A spun bearing would prevent oil to and from the port, the oil pressure is read from a spot at the back of the block on the chine wall next to the distributor.

A broken seized pump or intermediate shaft could be the problem or a blocked pick up.
Sorry about the details its on my brothers 440 we thought it might have been the oil pump or shaft we replaced that and had no luck still no oil pressure.