Thanks so much for the input guys! After sleeping on it and looking at my tools, it turns out that I have an angle die grinder. I should be able to use that, right?. I think I'll give welding a nut a try first though. Or will that only do more damage?

After I shoot some mig wire at it, should I use a propane or mapp torch around the surrounding area to expand it?

What penetrating oil do you guys recommend?I figure I need to start soaking it now.

I realize the head bolds and washers aren't ideal, but it's the way I bought it and like I said, I intend to swap some RHS's on this winter. I just want to drive this thing until then. I'll replace the bolts then.