O means Fairlane but often they interchange with Montego/Comet/Falcon. The Ford number will take precedence unless the other models use a unique part and will thus have their own coded number.
The Z following is for a "replacement" part. The original part will have a letter there that represents the system it comes from ie B for body E for electrical.
Z is the code for Mustang but only in the third digit spot hence a replacement part for a '67 Mustang will start with C7ZZ
And true often O parts are used in Mustang/Cougar
V is Lincoln and Y is the code for a replacement part for Lincoln only.
http://www.hammar.dyndns.org/~djhamma/partnumb.htm
Stu