The hydraulic parts are identical, so yes, the pump, valve block are interchangeable. The ECUs are electrically different, so you can only use a 2wd ECU on a 2wd loom, and a 4x4 ECU on a 4x4 loom. The 4x4 ECU's also programmed differently, so not suited to a 2wd application.

The wheel sensors I think are different at the front, not 100% on that though.

Most common faults are wheel sensors and the fluid level sensor in the cap.