QUOTE(Porschef @ Jul 1 2017, 03:34 AM)

-4 rotors are only what, 9mm wide? Your 5 lug rotors are probably in the 15mm range.
The Six rear rotors are almost exactly the same as the Four rear rotors. They are solid, not vented. They might be a mm or two thicker, but that doesn't prevent them from being used. They do have a slightly larger diameter, as has been mentioned, but that can be dealt with by turning them down or by spacing the caliper out a few mm.
Rear vented rotors are from some other car, typically a 911, and need appropriate calipers. The "V calipers" are 914 rears with a spacer in the middle so they can fit over the vented rotors, and others have used 911 rear brakes and either no parking brake or have modified the trailing arms to make the 911-type drum parking brake work.
--DD