First of all it does not have to be a 70Z pump. In fact if one failed Oliver did not furnish it for repairs. Next think The plunger is matched to the hydraulic head and never was available as a seperate part. Any hydraulic head off of any PSB pump from a 6 cylinder Oliver will work. The 70Z tells me you have an early diesel or the pump has been changed. I would like to have a picture of the broken plunger. Questions?