Have a 59 chevy apache 3100 with original 235. Lately I have noticed the oil pressure was really low, even when revving engine hard, may only get in mid 20's of pressure. I read the manuel and it wasn't much help. Will changing the oil pump be the solution for the oil pressure situation? Am also getting noise out of the bottom end of the motor, its been there ever since I had the head rebuilt due to oeverheating. Need some help here. Thanks.