track car is a broad term.
i believe the smart is already used in solo racing.
i don't think it is a serious drag contender.
smart competed in the one lap of america race.
it also won the
canonball run 2008
as to it's suitability for racing - just about anything with wheels has been raced.
i think at minimum you'd want ECU remap, suspension upgrades, tires.... different sanctioning bodies might require other mods like fuel cells or cages or taking out the glazing or whatever...