Paul,
I haven't found anything anywhere regarding the "Service Standards Manual" refered to in the 175 service handbook. Hopefully someone may have a copy and could post it? That is if it actually ever existed. May have been planned but never carried out.
I did at least find similar information for the 350's brakes, which are similar to the 175, under section 14, Tolerances and Fits:
standard Permissible Limit
5. Brake lining thickness 4.5mm (0.1772 inches) 2 mm (0.079 inches)
6. Brake shoes thickness 179.6–179.9mm (7.07–7.08 inches) 177mm (6.97 inches)
7. Brake drum inside diameter 180–180.2mm (7.09~7.095mm) 181mm(7.13 inches)
Interestingly, the 350's manual doesn't even mention the brakes in the text, nothing at all!
In general, the Bridgestone service manuals were pretty brief, and skip lightly over many areas without going into the detail I'd like. Oh well, they're the best we've got, and a million thanks to those who digitized them and made them available on this site!!!!!