Should take a 9/16" sized nut. The polished stainless would be a good way to go as the original types were known to de-laminate the chrome off the heads occasionally. Make sure the bracket faces are nice and flat at the bolt holes or you'll suck the blade in when you tighten the bolts. I'd also rustproof the back of the new blade to reduce rust issues- note I didn't say eliminate them.
