In many cases, an engine part may have several Service Part Numbers specific to Type Number and/or Code Number.If you do not find your specific Type Number next to any of the Service Part Numbers, the correct engine part number would default to the first (master) Service Part Number listed under that Reference Number. When the part is released for service it is assigned a Service part number. It is a different number, because how a part is finished and packaged for service is different from its original production counterpart. (It's the number used by your Ford parts man to look for your order. He doesn't want to know about the engineering part number.