That flat on the Bolt is there so the bolt can be inserted past the shock mount. The bolt threads into the control arm, to fix it will require a machine shop to bush the thread

I would soak the bolts with penetrating oil and be careful you don't snap them. When I did mine, I broke one bolt off in the trailing arm mount a real pain to fix.

To get the large bush off the body I cut the rubber then worried about removing the cup from the body.

 

Hi Warrjon

Those bolts with the half nuts look a real pain to undo, so I am also hoping that they don't Snap off, although on 'Vancouver's' schematic, instead of the Thread tapped into the Arm, its drilled right through and has a Nut on the end (which looks a much better idea)

As for the 'Big Ends' on the 'Trailing Arms' I made a 'Slide Hammer' out of some Scrap, which was pushed through the hole in the 'Rubber Bush' where it hooked on to the Inner Flange, right up against the Peg

Where because the Slide Hammer hit the Flange in just the right place, it only took a couple of 'Zonks' and the Trailing Arms came off dead easy

Making a Slide Hammer to take off the Trailing Arms

 

OB
The special bolts screws into a thread tapped into the suspension arm. There is no nut.