Hey! First of all nice car! Is that the one that was on ebay about 6 months ago? From S.California I believe?
Anyway, Are you 100% certain the car came with drums? If so, how do you know this?
It is possible that your car came with drums even though coded for disc's, I've seen it before but it's always been considered a factory mistake. The booster part# is the same for any disc brake E-body (except for Hemi) I'll try to get you a part# later.
The spindles themselves were always natural as cast steel. Some were dipped in cosmoline but this was only for temporary rust prevention while assembly took place, it usually wore off pretty fast and they rusted on the surface.