'Easing' is a bit of a euphemism I'm afraid. I wouldn't go drastically enlarging all the holes but if a gentle caress with a round file were enough to centre it, perhaps by removing any burrs then I would give it a go.
I might give that a try. I can't see how that would hurt anything.
This is a '73 roadster. My concern was that the end of the crankshaft stub was possibly bent, but I think I've ruled that out. The original Lucas alternator has a much sloppier fit clearance-wise than the aftermarket one.