NSX LM Road Car is not directly related to that NSX from Le Mans, is it?
If you consider that NSX to be a Lemans "road going", almost any street car with it's racing Le Mans counter part would be "a road going" version, right? Vipers, Mclarens, Corvettes, and so on.
To my knowledge, the only road going versions of Le Mans prototypes and that has been present in any incarnation of the game are the R390 Road Car, the GT One Road Car, and the CLK Road Car.