The wheel cylinder will only expand when you push the brake pedal which is not a good thing to do when you have no shoes installed. If you push on one piston a little the other piston should move out if it's not frozen.
all the guy at autozone had to do was to look at a drum for a 1978 to 88 Monte Carlo and it would tell you it's 9.5"
http://www.autozone.com/brakes-and-traction-control/brake-drum-rear/duralast-brake-drum-rear/22301_70093_0/
Does customer service actually exist anywhere in the automotive world anymore?
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