The back side is unpainted metal and so it will look grey in color. It does have white over-spray around the edges from when they painted the interior and so this is likely to be white you are seeing. The voltage regulator is a standard mustang one and you can get them at most Mustang stores. The best thing is to upgrade to a constant voltage regulator (better stability and reliability) and you can get them installed in the standard housing so they look original. When you talk about the washers, do you mean the little copper ones or the instrument retainers? I am guessing they could be found in places like wrecking yards, automotive stores and AMK as Ford was fairly standard with their hardware and they can be found on lots of cars.