Not looking to pile on $$, but this is a good time to swap in a fresh water pump easily. I learned that the hard way (is there any other way) just a few months after rebuilding my car's head. And you might want to search Sixto's postings on 603 head rebuilding, like in the one linked above. His guidance really worked for me. Good luck.

John

87 300TD #20 head 330K