Rear swing arm mounting brackets.

[HappyCamper]

While the engine and box are out, I started tidying up the rear end. It didn't look bad so I thought it was going to be an easy job. 
The inner swing arm mounts were okay, the nuts loosened and the bolts turn. The outside mounts are bad. The nuts come off, but the bolts won't turn. The outer side of the bracket is thin and won't take any abuse to get the bolt out. 
I see both Brickwerks and JK sell new brackets and I found some reference on here about replacing them. There was mention of making a jig to align the brackets, but I can't find any details of the jigs used or how this was done. 
Has anyone any advice on how to do this from experience. Although there is adjustment on the bracket, I presume they need to be pretty critical.

[tandemsandy]

Vinnie is back on the road this weekend after doing this very job (and a million other jobs). 
I cut the existing bolt out, then fabricated this, which replicates the bolt in-situ with a hard stop against the inner bracket flange.
https://photos.app.goo.gl/gbunve8bPeJe5sDC9

I tacked a bracket to the outrigger further inboard and could unbolt the fixture from there so it wasn't in the way when I cut the bracket from the end of the rotten outrigger & sill 
https://photos.app.goo.gl/y6QeyULnbHa53Dwp9

That allowed me to position the new bracket correctly in space and build the outrigger & sill to it
https://photos.app.goo.gl/9C2XTSBya5FFxfLp6

Am sure there's lots of other ways of doing it but this worked for me.

Rob