I have a wrecked FF3 that folded to one side in a rather bad T Bone accident, I should have discarded it, but that is against my nature, although it way beyond safe repair, I would be more than happy to part with it, as long as there was some sort of guarantee no attempt would be made to make it serviceable (well in someones eyes anyway) but it would seem the questions have been somewhat answered now.
With regard to the headstock casting, I took one to the ex-factory engineers, Furness and Searle for repair to see if they considered that possible, the bottom bearing housing was oval, and the bearing cup was accordingly loose, I seem to remember them telling me that it would easy enough to repair as it was a malleable casting, I think they simply put a bearing cup in the recess, and then beat the metal back to make a tight fit on the cup, whilst ensuring it went back also in alignment, I know it sounds awfully crude, but back in the day you just gave them jobs to do on Vincents, and trusted the results, it certainly seemed ok at the time.