Do you want convert to the GTs PBR dual piston calipers?
Like mentioned, to do that and use the rotors you would need to get them drilled for our bolt pattern, and the hub is a different size (but it is larger, so it will fit, but should have a hub centric ring). Probably be better off getting Thunderbird/Cougar non Sport rotors and using them if you want the dual piston calipers (which you never say you do, but I don't see wanting to use the rotor and pads only on a Mark VIII).
I went from the same brakes you have on my 97 Sport to the GT PBRs and I like them, but they aren't enough for me. I put the Sport brakes on my 89, and I don't know if I will put the GT PBRs on it when they become "spares" when the 97 gets the Cobra big brakes.