As you can see, I have not made them for all the cars but if you need help making others, I am happy to help.
From the readme
FILES HEREThese files add yellow and red segments to the tacho dial as shift indicators.
TachoMod for -
Cooper T81 A/B
Ferrari 312 A/B
Make a backup copy of cars66 folder just in case
Copy the supplied files to your installation.