The flat plug (Im assuming with a straight row of pins like the later 722.4 gearboxes)

is the simplest. the furthest two pins are the starter and the two pins near the edge where the wiring tube slips onto is the reverse lamp.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)