You'll find links for these below.
There are also community recommended apps in #suggest-a-mod
Car radar is a MUST HAVE : https://www.overtake.gg/downloads/car-radar.15743/
or there's one built into the Assetto Corsa App Shelf - guide to enable it here
Crew Chief : https://thecrewchief.org
Fuel calc : https://www.overtake.gg/downloads/cbv-fuel-calc.30852/
CMRT (BUT DISABLE THE STANDINGS PART OF IT AS THAT HAS A START COUNTDOWN WHICH IS AN UNFAIR ADVANTAGE): https://www.overtake.gg/downloads/cmrt-essential-hud.69475/
Race Essentials : https://raceessentials.wixsite.com/race-essentials
sub standings : https://www.overtake.gg/downloads/substanding-extended.51973/
Drone cam : https://www.overtake.gg/downloads/drone-camera.36405/
Camber Extravaganza : https://www.overtake.gg/downloads/camber-extravaganza.19703/
Track Map Display :https://www.overtake.gg/downloads/track-map-display-extended.51962/
Pro tires : https://www.overtake.gg/downloads/protyres.14030/