I'd heat the nut so it expands. Don't heat those coil springs by accident though.
You can get a box end wrench on there... but otherwise go get a cheap china impact deepwell and you'll be able to put your extension half way in. Then cheater pipe the breaker bar.
Can also try shocking it, get a box end or socket on there and have a buddy hold the thing in place while you get a solid kick to it. Using a wrench you can hit it with a hammer. Once it turns even just 1 degree, you're home free.
Don't forget the take it off one turn, then back a 1/4. It's time consuming but it cuts and clears the rust out of the threads making it so much easier in the long run. Then when you install it, add some washers so that you can actually hit it with a deepwell...
You can get a box end wrench on there... but otherwise go get a cheap china impact deepwell and you'll be able to put your extension half way in. Then cheater pipe the breaker bar.
Can also try shocking it, get a box end or socket on there and have a buddy hold the thing in place while you get a solid kick to it. Using a wrench you can hit it with a hammer. Once it turns even just 1 degree, you're home free.
Don't forget the take it off one turn, then back a 1/4. It's time consuming but it cuts and clears the rust out of the threads making it so much easier in the long run. Then when you install it, add some washers so that you can actually hit it with a deepwell...