rear swaybar

Hi, I have a broken sway bar axle bracket. The nuts are not the factory welded nuts. The bolts and nuts are not factory either. Tried to fit a 18mm box wrench but can't get it past the bolt to fit in the nut. Thought it would be an easy fix! 😂 Any idea on what to use?

Anyone familiar with plastic endlinks for the rear swaybar? I was looking to see if my endlinks needed to be replaced and found that I have something looking strikingly similar to this, although I can't confirm the bushings are polyurethane...