Ranger Mods

Hi,
My Name is Ralf 41 year old and just bought a new 3.2 wildtrack
I live in the south of germany and work as a mechanic! The last 4 years i had a Mazda cx5.
I already did some smaller changes with help of this forum!
Like climatecontrol, raptorlogo or carfinder.
In A few weeks i gonna start the project New tyres.
Planed is a 9x17 Et-6 with 285/70r17 bf goodrich tyres.
The Ford Dealer told me, its Not possible to adjust the spedometer! I have to use a extra electonic spedometer Tool (340€)
Here i found the exel form, but i hope to find more tips how to use?
My calculation told me
YYYY = 09DC tyresize : 285/70R17
Where is the maximum?

Also hope to See and Learn more about what is possible!

Thx

If automatic then max is 0977 for now and manual, change to 09DC which will work ok.

Still working with Forscan to try and resolve 0977 max in an auto.