Hy Mr. Lang, after having read this entire post, I think you probably have worn bearings where you have not already replaced them, cam bearings included in that. The oil pump provides oil into the oiling system, but it can only maintain pressure in the system if the clearances are not excessive and let the oil "bleed" out of the bearings too quickly. I doubt a new or rebuilt oil pump will cure your problem. If your engine is spewing oil out at high speed, that would indicate high crankcase pressure, that comes from excessive leakage past the piston rings. You said you have done a ring job recently, did you hone the block so the rings could "seat" to the cylinder walls? If you did not hone the block, or if you used "chrome" rings they will take a long time to "seat" if they "seat" at all, hope that helps.
