BBC long vs short water pump???

This is my first big block (a 454) and I have a few basic question which I will probably be posting over the next few months. Right now, I am shopping for a pulley set and do not know if my engine has a short or long water pump...

What is the differences? How can I tell them a part? Is one better than the other?

The short water pump measures 5-3/4" from the block surface to the hub. The long water pump is 7-5/16. Neither is better than the other except for conserving space.