This issue has persisted since the first Forza Motorsport on the original Xbox, despite the car not appearing in the Forza series for five years, between Horizon 1 and Motorsport 6. The FC3S RX-7 in Forza has a deformed and low quality model, as well as inaccurate bodykits. Despite my footage being taken from Forza Horizon 4, the model is still the same in Forza Motorsport, as is suggested by the LHD windshield wiper setup which was only correct in Forza Motorsport 1 (2005).
While the model compared here is an Infini, which has an extra front bumper splitter, it doesn’t change the rest of the body, at most the ride height.
The front bumper is stretched upwards, which is especially visible on the bottom bumper lights as they’re significantly oversized. The plastic trim, which on lower models is unpainted, goes at a wrong angle compared to real life. The entire front lacks smoothness, and all lights are of abysmal quality, as they’re basically opaque. The side window may be slightly too big. The whole rear end is inaccurate, taillights are inaccurately sized while the rear bumper is too large.
The side mirrors come from a USDM Turbo version from the same year, which would’ve been correct if the market version was never changed, because the FC3S originally appeared in FM1 as that USDM Turbo model.
Here is the FC3S RX-7 as it appears in Forza Motorsport 1 (2005)