If the pitting is pretty bad just get a set of Rare Spare Mirrors its not cheap restoring them ive got a few sets same thing all pitted.
Many chromers will not do the stems because they are cast so im told, there is a business in S.A. that removes the pitting and rechromes the stems like brand new a mate of mine had some done there.
About the swivel plates id like to know that to.?