The one in your link has 46mm spacing between mounting bolts.
The 650's is 44mm.
I bought one of these manual petcocks for my '78 KZ650 C2.
Haven't installed it yet, will in the Spring when I fire her up again.
Not the best looking fuel valve, but works well as confirmed by another 650 rider.
It goes on reserve much earlier though I hear.
EDIT: This petcock has failed on me.
At just under 500 KMs, when set to ON, it barley flows.
When set to OFF, it constantly drips.
The lever is getting hard to turn.
Ethanol in the gas may be a contributing factor.
Haven't taken apart the petcock yet.