This guide, and some other scattered places around the internet say you can use a MKIV golf caliper for the rears, which is true... But you can't use the bracket/slide from the Golf. Instead, if you do this you want the Audi A4/Volkswagen calipers of the same vintage. They are the same caliper as the Golf, but with a different mounting bracket. Those fit after drilling the factory brake caliper mounting plates, and putting a spacer in between the plate and the caliper bracket (washers do work, but will have people questioning your sanity). The brake hoses from the A4/Passat are also required (the end will match the hard lines on the AE86), unless you want to get custom ones. The discs required are Nissan P10 Primera/U13 Bluebird 258mm solid rotors with a 4 x 114.3 stud pattern - watch out that you don't get 4 x 100, Nissan made the exact same rotor with that stud pattern for other vehicles. From memory I think you need some hub centering rings too, the centre hole of the rotor is larger than on the AE86 axle.