Yeah, that sucks. I always remember the big cylinder bore and longer shoe to the front. Early ford brakes only, but that's all I tend to mess with. A lot of rear wheel cylinders get fitted backwards because the pipe run seems more natural entering from a forward direction. When fitted correctly the pipe enters from the rearward direction.
Check the other thread re rear wheel cylinders- there are a lot out there machined incorrectly which can leak right out of the box.