I agree with andrew, it would 'scare' me to have a mix match of parts from GM, etc. and different year/models of cars. How will you remember in 5 years which calipers, rotors or brake pads you need for maintenance or the poor guy that buys the car next. These are your brakes, I wouldn't mix parts like that and doing it right the first time is 1/2 as much $ as redoing it again, why redo them a few years later. Doing it right the first time doesn't cost anymore than the setup you're looking at. Try adding all the parts up new for that swap (bracket kit is $135 to start) as I wouldn't use used parts in brakes.
I would much prefer this original type setup for ~ the same $, less work as you don't have to change spindles/ tie rod ends (granada) which also adds the cost of a realignment $.
This kit also has upgraded pistons to avoid the corrosion that the originals suffer from for $525 if you are using manual brakes or there's an upgrade if you want a PB, etc. for $800. You could always add the PB at a later date to save money now.
http://www.discbrakeswap.com/Mustang%20Disc%20Brake%20Conversion%20Kits%20SWAP1 .html
Just my .02
Jon