What I ended up doing:
$ find /brickA -type f -exec md5sum "{}" + > brickA.txt $ find /brickB -type f -exec md5sum "{}" + > brickB.txt $ cut -c 1-32 brickA.txt > brickA_md5.txt $ grep -v -F -f brickA_md5.txt brickB.txt > onbrickB_notonbrickA.txt
Thanks for the help everyone.
Chris Murphy