It's much larger in all dimensions, becuase of the larger, with more offsset, backing plate.. It would probably be expensive to have a maching shop make one for you. Most S/Wagon, police cars, and taxi cabs had them. Probably a lot still around; it's just difficult trying to find someone willing to take the time to remove one for you.
IIRC, you'll also need the 'washer' (with the locking tab) that's used with the bolt. Shown in lower l/h corner in photo #2.
Also, the two backing plate bolts are longer.