10" Backing Plate Compatibility

[stop the beast]

My factory drums were 10 x 1.75 and I plan to use the guts with new shoes but I'm using the backing plates from an 8 3/4 housing because they are OEM with 5-bolt holes to mate to the 8 3/4 housing I've installed.

My question is will my 10 x 1.75 parts bolt up to this backing plate, it's slighty different? All mounting points/holes (for hardware etc) are the same. The difference is two little "tabs" on the welded on piece around the wheel cylinder. I have no idea what these are for in my setup or the larger 2 or 2.5 setup.

Check out the pics. All other features are identical between the old and new plates.

New plate, focus on the area right under the wheel cylinder cutout:

Old:

 

[stop the beast]

I'm guessing the old plates, orignally from my '66 Dart, were specific to the smaller 10 x 1.75 drums. The new ones are from a newer axle with the wider drums. I installed my 10 x 1.75 brakes on the new backing plates today with no issues. So, I guess it doesn't matter.