This is not a standalone mode, it requires Sk3lecreeper’s “Driveable AI” as well as Jazzycat’s classic pack to work
So far 28 vehicles from the classic pack were made drivable
This update features major improvement of vehicle stability at high speeds.
Top speeds are now higher as well, but it doesn't mean that Chieftain can now do 150 mph
Also two new vehicles are available:
Porsche 911 (1974-1989)
Beater version Ford Bronco 3rd-gen. (1980-1986)