The rusting problem is actually the inner steel sleeve of the rubber bushing.
It's likely gonna be rusted ( actually rust welded)to the the long bolt that goes through it.
You'll take off the nut, & use up all your strength trying to get that bolt to come out.
I even tried using a huge puller, & it kept slipping off. Even put the nut back on until it was flush with the end of the bolt, then hammering it.
PB blaster didn't even help. Once it finally moved a little, I was able to use prybars to get it a little further out. Then some blocks of wood to extend the prying action, saved the day.
Coat the new bolts with anti-seize, before putting them in!