A bit of clarification (again). When you order any item from a Ford service department, it will be listed with a "Z" in the forth position (C5AZ-) of the number. That is an inventory number. The "Z" signifies the item is controlled by the Ford service organization. It may be identified by a tag, a label or by the box it is in. That's the way you get it, even on e-bay. If the service department needs to order some more of those items, they will use that inventory number to make their order. Throughout the entire Ford system that number is used - right up to the time the actual part needs to be made. That final document says to make the item using a document having a part number that starts like this - C5AB- (an example). That document is referred to as the engineering drawing (by us at least), and will specify material, dimensions, process, finish among other aspics of making that item, including the marking of the item, which in most cases is the engineering number. It goes back up thru the Ford system identified with the previously mentioned tags, labels or boxes.
Jim