The specs might be in the archives. You could also mockup the axles and I think with the right axles in the right housing you want 1.5" between the ends of the axle splines. Add a bit for what you get for gap for the backing plate/foam/steel gaskets thicknesses & want 1.5" or to k.i.s.s. just slam the brake assy's together with the axles & measure the end gap there in the middle & likely you'll either be close to 1.5 or way off so it shouldn't be hard to get em matched