GT3 Cup and RSR are two very different cars ... one is really nothing more than a GT3 with slicks and strippped interior.

The RSR is a full blooded race machine, but my point was why not water down the RSR (A la GT1 Le Man's racer of the 90's). I'm sure for the street all you would need to do is:
- Add some crash foam and bumper supports to it'll pass NTSHA.
- Replace straight cut gears (Although I love the whine) with radial cut
- Add 6 speed instead of the sequential.
- Detune the engine to run on pump gas and be more reliable.
- Add cats and emissions crapola.
- Use silicone and rubber instead of metal bushings to soften the ride
- Raise the ride height 1.5 inches

All else remains the same and off you go.

It would make so much a better car than the GT3 RS in my opinion.