Some points of water intrusion,,,intake/exhaust manifold gasket, the headpipe gasket, the base gasket, (unlikely,,,unless the jugs are warped,,,),the head gasket,,,the top of the cylinders, (the head you have already shaved,, ), did you put a sealer on the head gasket ?,,,I chased a leaking head,,,ended up shaving lightly the head, putting on marine "perfect seal" on the head gasket, and adding an xtra 5 pounds of torque.