C-body 11in Drum to A-body 8 3/4 Questions

Are you using A body axles drilled to accept the big bolt pattern, or are you using re-splined/aftermarket big bolt pattern ones?

There are only 2 basic widths of fullsize 11" brakes, 2.5" and 3", the backing plates between the 2 ARE NOT interchangeable, as the depths are different.

FWIW, if you use the STOCK A body width housing with the large bolt conversion, you are actually widening the rear end by @ 3/4" over all.

The distance from the axle bearing to the the axle face is @ 3/8 wider on the large bolt axles.
This might be a problem with certain wheels on Darts.

To do it RIGHT, means a person SHOULD narrow a rear end and axles down the comparable difference.

Mark.