Per the Ford Car Parts book, there are two 289CID C4 tranmissions used on Mustangs in 1967, type PEE-C for non-HPs, and PEE-K for HP applications. I would assume the latter would apply to GT-350s also. There is no regular part number attached to the transmission (like C7ZB-7000-A) but shortend some what strange number that includes the assembly plant part number, a service level and build date code with the shift. Where did the C4ZR come from?
Jim