Ford Racing also offers a 1" dual master cylinder, that looks like the old style. The original application was an early 80's Crown Victoria or something. It is (or was) included in one of the Ford Racing brake kits for Fox body Mustang
http://www.fordracingparts.com/parts/part_details.asp?PartKeyField=7113
The SVO master cylinder is has a too large bore for many applications. SVO Mustangs came with big 73 mm / 2.87" calipers, hence the large 1 1/8" MC.
You need to look at the surface area of both the MC and the calipers when deciding on a MC for your disc brakes. Here's how different MC's and their surface area relate:
15/16" bore: 0.69 sq in
1" bore: 0.78 sq in
1 1/16" bore: 0.89 sq in
1 1/8" bore: 0.99 sq in
As you can see, the 1 1/8" MC is 44% larger than the 15/16" MC
Here's how different (front) calipers and their surface area relate:
stock 65-67 four piston (1 5/8"): 4.15 sq in
stock 68-73 single piston (2.38"): 4.44 sq in
Granada single piston (2.60"): 5.3 sq in
Mustang SVO single piston (73 mm/2.87"): 6.46 sq in
Cobra dual piston (40 mm): 3.89 sq in
Mustang GT 99+ dual piston (45 mm/1.77"): 4.92 sq in
There is of course more to a braking system than an MC and a pair of calipers, but it is important to keep the above surface area relations in consideration when putting together a braking system. Just because it physically fits, doesn't make it the right choice. If you neglect this, you end up with brakes that probably work, but not as good as they could.