There's a relatively easy opportunity for GC today on the team event, especially for single racer teams - Huracan overtaking. Use the Huracan LP610-4 in Automotive Mastery, and choose the Richmond 7 lap night race against 43 opponents. After I dumbed down the series by losing a speed snap 6 times, a fully serviced car got 105 overtakes in about 2:35, and even with the car in the red (16/28 upgrades), I am still managing between 75-88 overtakes per race, in about 2:45-2:50 (depending on bot shenanigans, of course). Just keep hitting Re-try at the end of the race to keep the same set of opposition.

2500 overtakes = 40 GC, so approximately 30 races at less than 3 mins each = decent return.
Good luck!