SBP Disc rotor ?

You have the correct discs, the sbp disc setups use a two piece hub and rotor. But i have no idea how to get them apart !

I'm facing the same thing, almost exactly, I just purchased a set of sbp discs for MY 68 Dart, I haven't bought new rotors yet but I need to.
Where did you buy your new discs ? and how much did they cost you ?