I still think they were anodized. I had a Clark Benson extrusion for a while, produced by Lionel, and incorrect because of that lower letterboard where there should have been flutes, and it was definitely anodized. I am a great fan of doing it the way you want, as opposed to preserving originality. If you want them polished, by all means polish them. A wire brush might not give you the finish you want.
If you get it all polished, and then discover you want the original look, a coat of dull clear lacquer will come close.
I mostly use Mac Shops Budd extrusions, and they come in raw aluminum. They must be polished about once every three or four years.
