Head Porting question

The most gains are to be found in the area just below the valve seat. Open them up to the valve seat width, then gasket match (it's not crucial that it be exact here) and open the pushrod pinch as much as possible with out going through the wall. If you do just JB weld or epoxy it back it up, it will be fine. If you really want to get fancy smooth the guide protrusion and give it a tear drop shape.