Thank you for your replies and email. Unfortunately, I have limited experience with Arduino and electronics alltogether.
Lakes:
Stereo usually only uses two cameras, is this for robotics use?
You are correct, but the build is for stereo lenticular photography, which requires more parallax than traditional two-view stereo cameras.
johnwasser:
Perhaps you will want a shield that can control four. Or you could get external stepper drivers (not a shield) and run wires to them.
I searched for Arduino Uno motor shields for more than two stepper motors, but couldn't find any.
I have decided to go another simpler route: two stepper motors w/ timing pulleys and belts. With that said, I don't believe I'll be needing to hire anymore.
Everyone on the Arduino Forum is always helpful and I appreciate it a lot! Thanks again!