Hey Rip, as far as I can tell from 89 and up they were just raw aluminum (Al-lu-min-e-um if your in the uk
)
That is interesting that you ask that because I have a set of hubs that I was thinking of doing the same thing to for my SM project.
I was even thinking about polishing them first, then clear powder coating, but I'm not sure how well it would hold up on the polished surface.
Hopefully someone here has tried it.....