Check out the rear disc brake installs for the FJ40, and you'll see what all parts were used to accomplish this mod. That caliper is pretty much the "standard" go to for this modification. The special bracket to hold the "metric" caliper is also typical. I've done this mod myself. There should also be a diverter valve very near the master cylinder going to the rear brakeline plumbing to lower the amount of fluid pressure to the rear caliper so that it won't lock up too soon.