McCauley governor model for '69 with a c6b?

[YankeeClipper]

The Woodward on the front just sheared itself to sprinkles so I'm trying to figure out where to go next. When I looked at the McCauley application guide (as a novice) I saw several governor numbers listed and didn't know where to go with that info.

Also wondering if it's worth it to find a used core for sale, and if it needs to be the same model, or if any Macaulay constant speed (or at least for any year of 337) would suffice as a core.

Thanks.