When the catalog states "stock width", they are referring to the housing dimensions, which in turn relates to the axle length from the tip of the splined end to the bearing shoulder.
Overall length is from tip of splined end to the outer face of the axle flange. Stock A body is 27 11/16". 28" aftermarket axles therefore give you 5/16" extra width per side (this extra width shows up as the distance the axle flange protrudes from the housing-i.e. "flange offset") which allows you to use the standard B, C, etc. 5 x 4.5 BC drums.
As far as which drums (10" or 11") to use, either will work fine. Some people don't like the extra weight of the 11s, some feel that the extra braking power offsets the extra weight in their particular setup. Your call. I run both- I have 10" drums on one car paired with 10.95 front discs, and run 11" drums on another paired with the 11.75 discs. Are they necessary? In my case, probably not; but I had them, so I used them- and they perform flawlessly. I have also considered swapping to the Jeep Grand Cherokee/Liberty rear discs, but I have a hard time justifying the replacement of something that already works well.