[dsraven]

backing plates can be swapped to match the brake set up you want, if that helps at all. yes, the cover will need to be removed to pull the "C" clips and release the axles but then wouldn't you wanna see what you have inside there anyway? take the carrier out and flush the housing and axle tubes, check bearings, check axle bearing wear surfaces, replace axle seals, etc etc?
if you just wanna see the size of shoes needed you can lay a flat edge bar across the axle flange and measure back to the backing plate, that will give a rough idea. knowing the wheel bolt pattern will vastly narrow down the possibilities as well.