I don't deal much with AutoCAD import/export, but, from my reading in these forums, I suspect the reason you haven't gotten an answer to this yet is that matching fonts between SW and AutoCAD seems to be one of those issues with no really good answers. Matching widths seems to be one of the worst areas. If it is not already in the Pet Peeves list, it should be.
That's what I was affraid of. Now if I can just convince those who are fighting this that font witdh doesn't make the drawing inaccurate.