Yeah that isn't going to work without a crap load of machining. you could get a kz1000/650/750 wheel and swap bearings perhaps. you would need new wheel spacers and your speedo wouldnt work. The rear drum, if properly set up, is ample for these little bikes. If you are worried about the old drum shoes falling apart get new ones. If it were my bike and i was wanting to upgrade the brakes I would just get a modern single disk setup. I think big single disks look freakin sweet and they are lighter than dual.
