Push rods can be checked for straight, if you have it down far enough to remove a lifter, then the push rods are out. Roll each one on a flat surface with your fingers in the middle. You can feel even a small bend. If I read the post correctly, you have changed the rocker arm shaft. Have you got good oil running at all the rocker arms? Have you looked close at the end of each rocker where it contacts the valve? Are they flat and smooth? Is there a worn spot on the valve stem? If you don't have good oil at the rockers you will get noise. If the valve stem or rocker arm are not smooth and flat, you will get noise. Any dirt or crud in the oil lines can cause all sorts of problems. Loss of oil to a lifter will let it collapse. Look close and let us know what you find.
