I use lots of PB Blaster,take the round adjuster washer off and lock washer and put the nut back on flush and a 10lb sledge hammer on a short handle and smack them out from the back. They usually come out pretty easy.
Going into the wheel well with a cutting torch is none fun! The rubber bushing burn/smoke/stink and smoke blocks view. A good fan helps. After you've cut/burned away as much as possible you'll likely still need a good crow bar to pry the arm out of the frame clips. What truly sux is going to so much trouble there then needing to weld the ball joint in because the threads in that bung failed. Good luck