In case you haven't found it because you haven't looked in Steam workshop (or don't visit nogrip where there's a download link for non-Steam clients), the 1960 Indy Roadsters are out there as of last night. This was a mod for rF1 (and, IMHO, let down by lack of a quality Indy) which has been nicely updated to rF2 quality. I've turned about 30 laps now and enjoyed them though I'm definitely a couple seconds off the pace. Note the special instructions for AI Strength (90%), AI Aggression (0%), and AI Limiter (0%). Really nice sounds. There are also tuning options before you go to the track.