I think you can use '68-'70 'Stang/Cougar front discs and may even use the '71-'73s as long as you take the whole spindle - you don't have to worry about different tie rods like the '65/'66 folks do. Beyond that I don't know how well the '77-'80 Granada/Monarch discs fits on the '70. With the '65/'66s they increase the front track width a bit and different outer tie rods need tobe used.
I think your best bet is 70-73 mustang/cougar. I seem to remember the spindle changing after 69 , but I'm not sure why , I think 70-73 may be beefier. Dont forget to get the BRAKE pedal out of the donor car. Brake pedals are different between drum and disc brakes. I think you might want to score the Vacuum booster and brake proportioning valve as well. Just my 2 cents.
The calipers from the 70 mustangs are far better than the others offered in earlier years. In my opinion the best thing to do is to go to a swap meet and find someone with 69-70 spindles and just bolt them up. It will look like it came from the factory when your done. I did this on mine already.
70fastback Modified 351W, front disc, auto -4 speed conv.
Actually the calipers from 68 to 73 are the same, 68-69 disc spindles are the same, 70-73 spindles are slightly beefier and take a different rotor(larger wheel bearings I think for the spindles).You will find Fairlanes of the same years with the same brake styles per mentioned the Mustang years.And don't forget the Mercury intermediates as well.One thing many people don't realize before doing granada swap, is the caliper and caliper mounting style is totally different from that used in Mustangs 68-73, and is easy to spot.I always think best alternative is to find the 68-73 stuff, at least visually they look nearly the same.
1967 S code GT Deluxe Coupe 65B
1966 Convertible 76B 289 4 speed
1964 Fairlane 500 2DR HT-the new project
1986 Jeep Cherokee 4X4 the "beater"