It doesn’t get much closer than this.
Watch as the driver of the Subaru WRX STI clearly indicates (as per track day rules) a clear path to pass to his fellow Subaru driver only for the pilot of a Ford Mustang Boss 302 to attempt to make the most of a fast closing gap.
The YouTube commentary reads: On a trackday at Mid American Motorplex, a point by was given for the blue STi, Boss 302 also tried to pass without getting a point by (point by was required for this race day). It ended up ok, but this has got to be the closest two cars can come without actually making contact.