Bad lifters or rod bearing? engine knocking?

It's a lifter/valve train noise and not a rod. How do I know? Because the noise is twice the speed of the RPM, which makes it camshaft related or valve train. If you've got the money and the engine is high mileage, put in a rebuilt, because of your oil pressure problem. If your budget is tight and the engine is low mileage, fix the lifter problem, get the oil pressure tested and if it's low replace the oil pump. Your money your decision. Good luck