i know for a fact that the looms and ecu are different.

2wd looms and ecu's come with either yellow or red connectors, and 4x4 are green. they cannot be interchanged as they have different pin layouts.

don't know about the pumps and valve block and stuff, perhaps stu would care to elaborate on his reply as he has experience.

i am using a 4x4 pump unit (with integrated valve block on LHD) with 2wd loom, ecu, sensors, and calipers