The MAF body and sensor are designed to match each other. Type A sensor works with Type A bodies. Therefore you can't swap sensors between different part number MAF bodies and maintain proper calibration. However, the bodies and sensors are not necessarily calibrated together to create a precision matched pair.
The output voltage of the MAF is a function of the air flowing through it. The MAF itself does not know about injector sizes, nor does it care. All it sees is that an increase in airflow means a corresponding increase of MAF output voltage. Altering the design of the MAF body can alter the flow past the sensor.
The OEM ford system was designed to use internal computer tables to match the voltage output of the MAF to a calculated injector turn on time. The injector table uses only one size injector in its calculations. This is a much more accurate means of determining the engine’s fuel requirements. Using a different MAF than the one the computer was designed for can upset the computer's calculations and the air/fuel ratio.
What aftermarket MAF’s do is try to fool the computer by either changing the amount of airflow over the stock electronics (C&L method) or by altering the sensor itself (Mass Air Systems method). The goal for both methods is to change the output voltage of the MAF so the computer calculates new data that is used to vary the pulse width sent to the injectors.
Unless I am mistaken, C&L tells you to use the MAF sensor that came with the original car. On a 89-93 5.0 Mustang, that was a E9ZF-12B579-xxx
