I know it's been a while... As a quick update, the Focus's standard Sync system is wired completely differently from the Mustang, apparently.
When my buddy and I tore apart my car and got it hooked up, we were able to run sync, but without any steering wheel controls or being able to plug in the new face plate do to different wiring. The Sync 3 APIM & screen wouldn't even turn on while the old Sync system was still plugged in.
Here's where the creativity comes... I decided that I didn't want to give up, so I purchased the entire wiring manual for all 2017 Ford Focus vehicles. I was able to trace which wires needed remapping or spliced in from other CANBUS connections (specifically for HVAC features).
Now, I haven't done the conversion yet, but I have it all remapped in a Google Sheet for everyone to check out if anyone is interested:
https://docs.google.com/spreadsheets/d/1gcnD6WD13f6KCUbdTTUSo0fGOTXCJtv5HmeemhjlwD8/edit?usp=sharing
This spreadsheet will soon be updated with pictures from the manual on each connector's pinout numbering so that anyone who is interested should be able to perform this upgrade (if I report success on getting it to work on my next forum post update).
I'm planning on doing the conversion this Sunday and will update afterwards.
Wish me luck!