On a 1967 Mustang is the longer shoe primary and does it go on toward front or back of rear brakes?

Yes, the longer brake shoe on a 1967 Mustang is the primary shoe and it goes towards the front of the rear brakes. The secondary shoe is shorter and goes towards the rear of the brakes. The primary shoe has a longer lining surface and does most of the braking work, while the secondary shoe helps to keep the shoes aligned and prevents them from chattering.