57 Merc rear axle needs backing plates & drums

I've got a 57 Mercury rear axle I'm sticking in my 26 Ford. The backing plates and brakes in general are not so good and I'm not having much luck finding parts to fix them. It is an old style big bearing flange with 5x5 wheel stud pattern. Anybody know of a newer backing plate/drum package that will fit this axle

 

Just curious because I'm not real familiar with the Mercs of that era. But did they go to the 9" rear end in '57 as did the Fords? If so, I would think you would have a wide range of backing plate and brake set-ups available. I would have just assumed the Mercs have them from '57 forward too. But the 5" bolt spacing has me wondering and surprises me. Not that it still couldn't be a 9" though. I've got a '58 Ford housing if you need measurements of the backing plate mounting flange for comparative measurements. Later pick-ups that still used the 9" used 5" bolt spacing I believe. Possibly some full size cars too, can't remember.