I have rebuilt far too many heads in my day. See if you can determine a model number for your Wilcox and head (no pun intended) down to your local West Marine and buy the rebuild kit. I can almost guarantee that one is available. The project may take an hour or two but it is typically not that challenging. You disassemble the pump and replace the worn rubber parts with the parts from the kit. Just mind the placement of the joker valve and you will be all set. Good luck.