Erik - I think if you look in your shop manual you'll find the secondary shoe [front of each wheel] is supposed to be shorter than the primary shoe .... the general intended it that way, if you previously had shoes with the same length linings, somebody goofed
the thickness of the linings is likely to have to do with whether they're bonded or riveted, riveted shoes will be thicker material to give the same wear depth and still leave enough material for the rivets to hold
Bill
