Perry,
If you are talking about simply the cast-iron exhaust manifold, I don't believe they were "finished" per se. Thus, correctly finishing them would be to do nothing.
Now, that being said, perhaps you'd like to maintain that just-cast look that fresh iron has before rust sets in.
Go to the Eastwood catalog, they have a variety of finishes available that mimic cast iron and will allow you to maintain the look without rust.
I also believe there is a special, high-temperature powder coat available (
www.jet-hot.com) that you could use if the manifold is off the car and you send it out.
Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored