Since the process went well, I thought I would share my experiences here, should any of you be interested in doing something similar. Total cost to me was $320 including shipping costs.
The unit I got my hands on is the Zestech PX6 - 4GB RAM, 64GB ROM, 10.1" IPS display (my Hilux is the right hand drive model), this should make no difference with the left hand version as the only change would be the "frame/mount" for the unit, the android system & wiring should be the same. Part of the wiring harness includes two usb cables. You can find this PX6 unit on Alibaba.
Features I have tested & can confirm works:
1) Bluetooth, imported the phonebook & made calls
2) GPS - Installed Sygic (the head unit comes with a small external gps as it cannot connect directly to the Hilux factory GPS)
3) Android Auto, Automate, etc (really cool applications to use as a launcher for the unit)
4) WiFi connection
5) Radio
I am still trying to investigate how to view vehicle stats (similar to how the stock unit does range & economy), this is by no means a critical feature.
I will be testing the android screen mirroring as the unit is capable of this both wirelessly as well as USB.
This hardware installation is pretty much plug & play, there are wiring harnesses with a bunch of extra connectors. You would just need to connect:
1) The AUX cables together
2) Camera to REV-V
3) Canbus box to the head unit connector
4) Steering buttons are mapped to the unit software (via a learning application - easy to do)
5) Remaining standard connectors to the Hilux (power,etc)
Update 26/09/19 - I am investigating using the OEM GPS with the new head unit. I have ordered some new connectors & will try to make up a cable that does not involve cutting the OEM wiring harness. In theory this should work, will keep you posted.
Final Product:
