or....if you've got fork legs that have the mounts for these brackets/calipers then why not go for something way way better than rubbish 70's technology, admittedly in themselves far better than earlier 750 swinging single piston calipers.
the only limitation to what you can use is the space between the fork leg and the spokes of the wire wheel. I've managed to get a proper 4 piston Braking brand caliper onto mine ( using CB900 fork lowers ), its a super motard racing one so it works well with the spoked wheel. it has required me to make one tiny little bracket about 4cm long ( or inch and a half in measurements of the dead ) to space the trailing edge of the caliper out from the disc ( the VFR800 one mentioned below )
and if originality isn't a worry , which if you're upgrading the brakes i'm guessing it isn't then a VFR800 disc will fit with minimal work then you get the best of both worlds, a thinner, lighter, bigger disc thats vented with a caliper that was designed to actually stop a bike rather than suggesting a marginal impediment to forward motion
I've done the conversion before using a CX650E caliper and the difference was remarkable.
i used the same approach on my Vmax, got rid of the stock (heavy, vented, small ) discs and absolutely rubbish twin opposed piston calipers and replaced them with 310mm R1 discs and hayabusa 6 piston calipers. i no longer fear imminent death on that bike ( unless i press my luck in the forward motion on a loose surface kind of thing )
