Got a tumbler?
Couple of hours in a tumbler and it will work itself out
+1 - assuming there's no locktite in there!
Easyout's will work. If you have a mechanic mate, they always have lots in all different sizes.
Call Dr Bolt or Captain Thread, those guys are legends they will come to your house.
They have all the latest gear to get threads out and they make it look easy, reasonable prices too.
