Might want to check here
Toyota 4WD Surf Owners :: Index
I would think there would be a ground, then three wires min to engage 2hi, 4hi and 4low.
B+ would come from the instrument panel I suppose in a stock truck.
Anyway, that tranny is pretty common in the diesel Surf from what I quicky read. Use that link and see where it takes you in terms of information.
I am sure those fellows will have a wiring diagram for the truck/chassis/driveline.