Rear Disc Brake Kit From Summit

when replacement pads or further down the road and rotors or calipers are needed, does anyone know if the Summitt or Dr Diff rear disk components for the 8 3/4 rears cross reference to standard replacement parts, or or do you need to go back and pay Summitt or the Doctor every time a new part is needed?

and

do these kits work on the original A body 8 3/4 sbp redrilled to lbp axels, or only the new ones? I saw where there is flange width difference on the original SBP 8 3/4 axels, or does this not make a difference with a disk brake package.

thanks