its a straight swap however,
The handbrake bracketry mounts differently, you will need to keep the hand brake bracket, the 2 long bolts and spacers and the 2 short bolts that mount the rear of the hand brake bracket. These are all M8 bolts. You can either swap the rear output bearing housong of the transfer box for your defender one which will have the 2 rear holes for the Hb bracket or drill and tap new threads iin the discovery box this must be done carefully not too deep. Jai