I assume you are fitting the bracket to 1600/180B rear control arms
Like you I tried to go hi tech. with this job.
In the end sanity prevailed and I bought a circular grindstone which fit inside the original hole.
Set the grindstone into my drill press and gently moved the bracket around on the platform and enlarged the hole
Use the drum brake backing plate to mark the new diameter on the R31 bracket.
From memory, it is only a few mm and it is not super critical to fit on the hub snugly.
Get the largest diameter stone you can and it will do the job without leaving lots of little gouges in the circumference of the hole
A die grinder would also work but because of its small diameter, the hole gets pretty rough and needs grinding anyway to smooth it up
Once it is large enough to slip over the hub you can then make any minor adjustments for it to sit flat against the hub flange

_________________
Regards, Graeme
Just trying to help...
http://nissanman.shutterfly.com/
graemes@internode.on.net

gas axe it yourself, u can get a nice cut with a bit of practice, granted not as good as lasercut.
or you if you hav access to a plasma cutter.
or you could just spend a bit of mula and pay sum1 to do it??

Laser brackets are available for R31 conversions

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A little knowledge is a dangerous thing.
www.datsport.com

"R.I.P. Baz. 29 April 2022. Thank you for all your contributions to the Datsun community over the years. You will be missed." - OZDAT

I just used a drill fitted with a rotary file and finished it with a stone. You've only got to enlarge it 1.5-2mm in diameter for a 1600.

Cheers,

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Chris [;-{)>