I used 93 jeep Cherokee rotors. You don't need a measurement to place the caliper bracket. Just bolt on the rotors put the pads in the calipers and bolt them to the brackets. Install them over the rotor and it helps if you have someone hold the brake pedal one you have them where you want them, this will square them up to the rotor. Then just tack the brackets on, remove everything and weld them up. Here's some pics from mine.