Thank you for your interest in Water Pumps Direct. The ONLY difference between a 2-wire and 3-wire pump is that the 3-wire pump requires the control box, which houses the pump relay, overload and capacitor. The 2-wire pumps include all starting components inside the pump. Thus, if you are installing a 2-wire pump, there is no need for the control box and you should NOT include it in any portion of your installation.
If one was to use a control box that was already installed, you only need to insure that the horsepower (HP) rating of the pump and control box match.