Range/variation, call it what you want. An example of Ford's acceptable range would be 113-150psi on the same motor. Obviously that's not very helpful as I'd be pulling a motor apart long before it was that bad.
112-120 is poor. Make sure your gauge is accurate and the motor is at least somewhat warm. Also make sure that you have the throttle open, the injectors disabled and a strong battery. With only 5psi variation it doesn't seem right that they would all be that low unless the rings are just that badly worn out. Try squirting some oil into a cylinder and see if the compression jumps up a whole bunch. Since you know that all the cylinders are even, just test one out and see what happens.