Thanks, Doc. I'll have to call them (and PST) for details.
They look the same, except Dr. Diff has no MC for A body w/ man brakes (mine), no control arms and ball joints, and no adjustable proportioning valve, unless the distribution valve is for that purpose. If that's the case, it won't work because my GM rear drums will require adjustable F-R bias.
The $435 goes up a bunch when I add the items PST includes.
PST has free shipping, Dr. Diff $293.00!