I don't know how you can clean up the sanding you did to it, but i know that if you take bleach it will clean up and whiten the surface of the headlight. If you can, take off the lens and clean it inside and out with bleach. A friend of mine did this to his tail lenses on his POS VW Corrado and they were ALOT clearer and nicer. Good luck!
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previous name: 84stangLX
'84 Mustang 5.0 LX
my LX
'89 Mustang GT
my GT