Hi guys,
the G-model is absolutely unknown to be.
Just collected these information over time:
http://www.z750twin.de/1980_g-modell.htm
Have a look into that page and scroll down. There is the only G-model shown that I have ever seen live. It is from Germany and the owner fitted the LTD spoked wheels. That may be an option ?
Be aware of front fork (axle right below it).
That has influence on the yokes to choose and the brake caliper holders and discs as well.
All the best,
Michael
PS: Found some more pics of that Twin:
