Gus,
Yes, the brackets are designed for the standard 2wd rear disc, which I believe from memory is 273mm.

It can also accomodate the 4x4 disc which is the same size, but vented. This would obviously require the 4x4 calipers, which use a wider carrier.

Any caliper from the Sierra / Granada range with solid discs can be sourced from the scrapyard to use for this.

It is recommended that you also use a bias valve or get the load compensator adjusted to suit (SCC do this).
Best regards