Hey, Robert,
     Did the same thing, turned out to be that my rear brakes weren't
self-adjusting themselves.  They are a PITA, and I haven't yet figured out
how to adjust them through the little hole.  My experience included replacing
the drums (they needed it) and shoes, this is why I was rather upset at
having squishy pedal.  Taking off the drums and snugging them up made all the
difference.  Also, clean and lube all the little parts that make up the
adjusters.  PO had them on wrong.  Firm pedal now.

Hope it helps,
Bill Marshall