Pump selection depends on what flow & pressure will be required by the hydraulic system, i.e., how fast the cylinder or motor should run and how much force or torque it must develop. Then a pump can be selected which is capable of that flow & pressure. And then an engine or motor can be selected which is capable of driving that pump with sufficient power.
Selecting components for a hydraulic system can get complicated. We have a lot of experience replacing system components or building new ones. We’ll be happy to help you get the right one.