How many sensors are there on the box. I would have a guess it's about 3.
Vehicle Speed Sensor 2
Neutral Position Switch
Reverse Selection Sensor
So you could work out whats what selecting reverse and checking which one makes/breaks contact, the same for the Neutral and then logically that just leaves the speed sensor.
That identifies the sensors, then just buzz the ECU side of the loom through in accordance with the below ECU pin out, although Referse switch will go to light circuit not ECU.
http://www.jollygreenmonster.com/pinouts.htm