Gran Turismo Red Bull X2011 Prototype
Toyota GT-One Race Car '99
Gran Turismo Red Bull X2010 Prototype
Gran Turismo Red Bull X2010
Gran Turismo Red Bull X2010 S.VETTEL
Bentley Speed 8 Race Car '03
Peugeot 908 HDi FAP - Team Oreca Matmut '10
Peugeot 908 HDi FAP - Team Peugeot Total '10
Audi R8 Race Car '01
Pescarolo C60 Hybride - Judd Race Car '05
Audi R8 Race Car (Audi Playstation Team Oreca) '05
Nissan R92CP Race Car '92
Bugatti Veyron 16.4 '09
The cars above are all capable of 300+mph on the 10'000m (SSRX).
If you do a flying start, then the following cars should be fast enough to break the 300mph mark too:
BMW V12 LMR
Toyota Minolta 88C-V Race Car '89
Pescarolo Courage Judd GVS Race Car '04
Mercedes Benz Sauber Mercedes C9 Race Car '89
EDIT: Perhaps a Mazda 787b too