Alternator resoration.

As I have my motor apart ('70E), I feel compeled to go through the alternator. It is Bosch, and the exterior is a real mess- very badly corroded. I have partially disassembled it. the inside of the alternator body seems to have a black finish. the body seems very light. Is it magnesium? I'd like to bead blast the body and apply some correct finish if appropriate. At the same time I'll paint the outside of the magnet. In addition I'll address functional issues of bearings, brushes, etc. Anybody done anything like this? I just don't want to send it out for a rebuild and have it return with poor and/or incorrect finishes. Any information on the original finishes would be greatly appreciated.
-Scott

Hi Scott,
If no else has an answer for you the following firm in CA does nothing but Bosch. They have been friendly to me in the past with answers to my questions.

Bosch Alternator and Starter Rebuilds
562-944-3221
Jim

Jim-
Thanks for the tip. Sounds like a good resource.
-Scott