gpz rear hub widths.

I'm looking to put a GPZ rear wheel on one of my projects. My current GSXR rear wheel is too wide, and I need a 18" that matches the front. The 3 spoke gpz style is very similar, found on the 550, 750 and 900. I was wondering if you guys know what the overall hub widths are on the models (disc to drive), and if there is any swapping to slimmer hubs?

Thanks

My 550 (which is the same as a 750) is approx 260mm inside of swingarm. Maybe a couple mm less. The straight secion of the axle (w/out threads) is 275mm.

I wonder how much of that is taken up by spacers and caliper mounting?