The centres of the discs are different, as in where they attach to the wheels. The FZ6 front discs only match the FZS1000 / R1 front wheel, not the FZS600.
Having said that, the diameter of the discs are the same, hence some confusion.
There are however other mid '90s Yamahas to pick from, such as TDM 850, TRX850 & Thundercat if I'm not mistaken