It looks a lot worse in that photo because of the condensation because it was fresh out of the freezer.
The dents in the expansion are all but out so I think I'm going to tack a nut into the dents near the exhaust port and use my slide hammer to get them out. As far as the rust I'm going steel wool the shit out of it. I have scotch brite wheels for my dremel I might try too.
"I've got a message in a bottle, written in gas and oil, signed with a rag and a match"