When there is a difference in length of material, the shorter goes to the front and the longer to the rear. If there is no difference in length, but a difference in material color, the lighter shoes goes to the front, and the darker to the rear.

It doesn't matter if we are talking about rear or front drum brakes.

When there is no fixed lower anchor (as the case with the era of Mopars generally being discussed here), the front/primary shoe's main job is to apply the rear/secondary shoe, which does the lion's share of the braking.