74 Dart Disc Brake Conversion
I have performed this conversion several times. Since the 75 Valiant has the steering components you need, just purchase new rotors and rebuilt calipers. Try to find loaded calipers. Loaded units come with all the hardware needed to install and new brake pads too. If you can't find loaded units you will have to purchase the holdown plates and bolts and the bolts that mount the calipers to the spindles. Your also going to need to need new wheels bearings and grease seals. I don't know the availability of these parts in Canada, but they're very readily availble here. Try undercar.com or Rare parts.com. they will direct ship to you. Hope this helps.
HemimanDan