Is the parking brake fully released? It sounds like the strut that fits between the shoes just below the wheel cylinder is the culprit, not the wheel cylinder. Be sure there's no tension on the park brake cables, which would pull the lever arm attached to the rear shoe toward the front slightly and cause the strut to push on the front shoe. I've seen that happen pretty frequently. You're running Bendix-type brakes with one adjuster wheel at the bottom, right?
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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