I decided to make an additional mount to help guide the handbrake cable. There is already a P-Clip under the brake pipe Tee piece, but I thought it would help having one on the diff.
The hole is a M12 x 1.5mm thread. I started with a standard M12 x 1.75mm bolt (65mm long to get a long enough shank). I cut off the threaded part and faced off the end of the bolt in the lathe. I put on a 45 degree chamfer to assist the thread die. I then threaded the shank.
I drilled a 4.2mm hole in the head end of the bolt and I tapped it to M5.
I put in place a 17mm P-clip and I will adjust the rotation once the cable is fully installed.