I've contacted two different honda shops in my area. Both tell me the mount pattern is different between the 750c and 750k. Mainly because they have different swingarm designs.
On the plus side, the 750k and 750f have the same swingarm and part number for the chain guard.
'81 Honda CB750K
'74 Moto Guzzi Eldorado (LAPD)
'08 Kawasaki Nomad 1600