Ok, I think I am getting somewhere on this, I just got my SVT rear brakes today and you can see the difference
in the brackets:
You can see the main difference is the location of the two bolt holes that attach the bracket to the spindle.
On the SVT brackets the bolt holes are down at the corners of the "U" shape, compared to the other bracket,
where the holes are further up. After a lot of measuring the brackets are otherwise the same, the holes just
push the bracket about 10mm further out (which makes sense since the brake rotors on the SVT are 280mm
and 260mm on the regular models with rear discs.
Talking to Steve at Tousley, I found there are two basic rear discs available from Ford for the Focus, 280mm and 260mm.
Looks like I will be selling my 260mm brackets and calipers in the For Sale section...
...learned a lot, hope this is useful to somebody...
2003 ZTW, 2.3L, auto, soon to be 300/280 SVT discs...