Ok, let me be clear, I'm not trying to argue, I'm just siting my source.
At the end of the Fuel System section of the Ford 1965 Comet, Falcon, Fairlane and Mustang Shop Manual (the one with the red cover) there is an Application Chart.
It lists C4ZF-E & F for 260 engines.
It lists C4GF-AE & AF, C5ZF-C, D, E, & F for 289 engines. Mine being Oct '64, seems like the C4GF would be appropriate. But I will defer to the experts.
Looking at the mustangtek chart, I'm confused about all the references to 64 & 64.5 289 applications. Maybe my Mustang trivia has become fuzzy over the years, but I thought 64.5 = 260 (other than HiPo) and 65 = 289?