To Chuck and all. Yes, I would very much like to get pictures of flywheel markings -- whole flywheel, the close up of casting number/date code, and marking along the perimeter -- in high resolution JPEGs. (My email is bobmannel@charter.net.) For HiPos, there are two castings -- C3OE-6380-B and C6ZE-6380-A. The former will also have a circled C outboard from the counterweight. The latter will have a C7ZE-A stamped into the perimeter. The standard 289 used the same casting -- the earlier one will have no circled letter stamping, the latter one will be stamped C7ZE-B. And, if you find a C3OE-6380-B casting with a circled A, it was used for the 1964 260. Some of this is verified, but I am working on getting a bigger data sampling. It is all about how the flywheels were imbalanced. The 260 was 26.2, 289 was 28.2, and the 289 HiPo was 30.4 ounce-inches.
I am working on a CD version of my book "Mustang & Ford Small Blook V8, 1962-1969". It will incorporate all the corrections and include supplemental information. I did not cover flywheels in the book, but will do so in the CD version. Can't give you a time of availability yet. These things take time.