head casting # on 2003 Chevrolet Malibu

Where do I find the head casting numbers? I'm going to get the heads rebuilt and the shop wants those numbers and if the rockers are 8 or 10mm, how do I find out that?

Asked by for the 2003 Chevrolet Malibu
2003 Chevrolet Malibu 3.1L SFI OHV 6cyl Could be located under the valve cover or cast into the ends or sides of the heads and to get to the rockers the valve cover needs to be removed. Go to and sign up there is a complete cylinder head removal guide there.