Those are MGR numbers that Nich gave you. Essentially the front discs and calipers are the same as the ZT 190 (and the BMW 330 actually), but since the calipers are mounted trailing on the V8's, you use the ZT 190 left caliper on the right of the car for the ZT 260 and the ZT 190 right caliper on the left.
Rover 75 V8 and MG ZT 260 are the same.

David