Small to large bolt pattern swap
There is no direct fit rotor, but from appearances the SSBC rotor looks like a 65-67 Mustang piece with a spacer for the bearings, which are the same, but the offset is slightly different. The calipers used are the same casting, but machined differently.
The reason this is not a popular swap attempted is that too many people are afraid of the K-H caliper and the four pistons. The rotor is also considerably thinner than the late unicast rotor.