HRL's puller idea is a good one but with all that rust I'm not sure if you wouldn't just tear the head off that spring mount if you get too medieval. It still might be worth a try to apply heat and some PB and give it some reasonable tugs/taps with a slide hammer to see if you can get any movement. But if that fails, X2 on the cutoff wheel. If the nut/bolt spins freely you will have to slice the nut in half to free it from the bolt. Get the thinnest wheel you can and go for it. Good luck.
SimS
