All of the pressure is on the cam caps, all of the wear will be on the caps, the valve spring pressure always pushes the cams up, the only places you will likely see wear on the bottom is the journels closest to the cam chain as it pulls the cams down. I would run it provided the cap looks good and clearances check out. Kind of looks like the surface was etched from moisture or acids in old engine oil after sitting for a long time.