Plans
You can purchase plans for your 9 from Van’s $10 on a thumb drive.
Obviously the backing plates are riveted to the pad. Likely you have Matco brakes. Wheels are 5:00 x 5 . A call to Vans support can likely give you a part number for backing plate. You should verify brand of your brakes, previous owner builder could have used something different. Enjoy tinkering with your 9!