With your new pump installed, prime the pump with the drill motor in reverse, use the proper hex priming rod counter clock wise. Try priming the engine, if you get little or no oil pressure then you pull off the valve covers , check to see if any rockers are broken, check to see if all the push rods are seated properly. It sounds to me that a push rod dropped of and a lifter popped out of the bore causing the loss of oil pressure. Hopefully that is all.