First off let me say, if you have the means to do this yourself then go for it otherwise it isn't worth it to pay someone to do the machine work. I did some bartering with a local guy who turned out to be a machinist and cut me a great deal. For the going hourly rate for this job he told me he would have charged me $700. I loaned him my Eastwood fender lip roller.
Originally I though I could use the hub the same way the MustangSteve kit works:
The Granada rotor has a longer body that the vintage hubs so running the 13 rotor over the outside of the Granada hub would have required very long bolts for the caliper mount/anchor. This would have put dangerous force on the ends of these two bolts during braking. I even thought about using components of a Wilwood Mustang II/Pinto big brake kit that use a hub that would fit on a Granada spindle. That was way too expensive and not as fun as doing it myself.
Started with new Granada rotors, I wanted to make sure I was getting a pair of fairly equal thickness hubs coming from the same factory.
Marked for cutting
Hub Machined; center cut down and flange smoothed and leveled
Center bore of 13" rotor also machined to slip over the inner wheel bearing shaft
Here's how I bolted the spacer on, I started with a 1.5" adapter with press in studs. I pressed the studs out and am using longer Grade 8 studs, Torque the spacer to the hub/rotor using the recessed holes and the stud extends beyond the spacer allowing for the wheel to bolt to it.
Test fit 17x9
1" flare needed
Mock up of the brakes, the image is slanted, didn't level the camera