Tony : To explain a little further in what John has just presented (as well as for those that may not know the "Total Part Number" deciphering, here is a little more to wet your whistle.
Using the following as a generic Part Number, and using lower case letters for the generic to distinguish between the generic and actual Part Numbers which used all caps, here is a breakdown :
Part Number - abcd-efghijk-l
a = Decade (Ford began this system of Part Numbering in 1950, starting with "B".
b = Year of the decade (0 through 9)
c = Model for which Part was originally designed (see table below)
d = Engineering Division for which Part was Designed (see second table below)
efghijk = Group Number that Part fits into ( see attachments 3,4 and 5) - this could be 4 to 7 characters long, and could include the body type preceding the Group Number if a
part was designed only for a specific body type of the Model listed. For example, a C7ZZ- 63xxxxx would be a Ford Service Part designed for a 1967 Mustang Fastback.
l = Design Version or Change
The Part Number represents the Model the particular part was originally designed for. As John noted, many times the same exact part was used for other Models, and thus you many times see Mustang Parts that are C7A-, C7S-, etc.
Taking into account all of the above, the Power Brake Booster sown in attachment # 6, C7WA-2005-B, was originally designed as a Lincoln/Mercury Chassis Part for a 1967 Cougar, but may have other applications for which it will work.
Hope this will be of help.
Bob