I have been told that the rear diff head from a d21 Terrano v6 -it must be v6- with 31 spline will fit, and if the ratio is incorrect you can use the carrier to fit to your front diff.
I have done it to a '93 Safari and it was the RED wire .Pull out the speedo & cut the wire (it is a very small diameter wire)& put a piece of twinflex (Iused speaker wire)to connect either side then route the twinflex somewhere discrete & fit a toggle switch