Here are the road cars that I've found to be able to break 300 mph (fully tuned and with Nitrous, no draft). Feel free to help me expand it, though proof of the car breaking 300 mph is needed before I'll add it to the list.
- Alfa Romeo TZ3 Stradale '11 (1206 hp)
- Aston Martin One 77 '11 (1221 hp)
- Audi Le Mans quattro '03 (969 hp)
- Audi R8 4.2 FSI R tronic '07 (959 hp)
- Audi R8 5.2 FSI quattro '09 (1141 hp)
- Bugatti Veyron 16.4 '09 (1324 hp)
- Bugatti Veyron 16.4 '13 (1324 hp)
- BMW M4 Coupe '14 (~1050 hp)
- BMW M4 M Performance Edition '14 (1015 hp)
- Cadillac Cien '02 (1045 hp)
- Chevrolet Corvette C7 Test Prototype (913 hp)
- Chevrolet Corvette Stingray (C7) '14 (920 hp)
- Chevrolet Corvette Stingray Gran Turismo Concept '13 (920 hp)
- Chevrolet Corvette Z06 (C5) '00 (802 hp)
- Chevrolet Corvette Z06 (C5) '04 (847 hp)
- Chevrolet Corvette Z06 (C6) '06 (919 hp)
- Chevrolet Corvette ZR-1 (C4) '90 (811 hp)
- Chevrolet Corvette ZR1 (C6) '09 (1050 hp)
- Citroen GT by Citroen Road Car (943 hp)
- Ferrari Enzo '02 (979 hp)
- Ferrari FXX '07 (1138 hp)
- Ferrari GTO '84 (879 hp)
- Ford GT '05 (940 hp)
- Ford GT '06 (940 hp)
- Ford GT Concept '02 (948 hp)
- Ford GT40 Mark I '66 (833 hp)
- Lamborghini Aventador LP 700-4 '11 (956 hp)
- Lamborghini Diablo GT '00 (1056 hp)
- Lamborghini Gallardo LP 560-4 '08 (799 hp)
- Lamborghini Murcielago LP 640 '09 (928 hp)
- Lamborghini Murciélago LP 640 Chrome Line '09 (928 hp)
- Lamborghini Murcielago LP 670-4 SuperVeloce '09 (928 hp)
- Lamborghini Reventon '08 (1039 hp)
- Light Car Company Rocket '07 (353 hp)
- Lotus Esprit Sport 350 '00 (950 hp)
- Lotus Esprit V8 '02 (928 hp)
- Lotus Esprit V8 GT '98 (916 hp)
- Lotus Esprit V8 SE '98 (916 hp)
- McLaren F1 '94 (937 hp)
- McLaren MP4-12C '10 (973 hp)
- Mercedes SLR McLaren '03 (997 hp)
- Mercedes-Benz AMG Vision GT (1101 hp)
- Mercedes-Benz C 63 AMG '08 (1050 hp)
- Mercedes-Benz SL 55 AMG (R230) '02 (865 hp)
- Mercedes-Benz SL 600 (R230) '04 (1012 hp)
- Mercedes-Benz SL 65 AMG (R230) '04 (1051 hp)
- Mercedes-Benz SLR McLaren '09 (1005 hp)
- Mercedes-Benz SLS AMG '10 (842 hp)
- Mitsubishi GTO TwinTurbo MR '98 (938 hp)
- Mitsubishi HSR-II '89 (699 hp)
- Nissan 300ZX 2by2 (Z32) '98 (902 hp)
- Nissan 300ZX 2seater (Z32) '89 (832 hp)
- Nissan 300ZX 2seater (Z32) '98 (902 hp)
- Nissan 300ZX TwinTurbo 2seater (Z32) '98 (873 hp)
- Nissan Fairlady Z 300 ZX Version S TwinTurbo 2seater (Z32) '98 (902 hp)
- Nissan Fairlady Z 300ZX (Z31) '83 (678 hp)
- Nissan Fairlady Z 300ZX Version R Twin Turbo 2by2 (Z32) '98 (902 hp)
- Nissan GT-R '07 (1020 hp)
- Nissan GT-R Black edition '12 (1121 hp)
- Nissan GT-R Black Mask '07 (1035 hp)
- Nissan GT-R Concept (Tokyo Motor Show) '01 (951 hp)
- Nissan GT-R NISMO '14 (1170 hp)
- Nissan GT-R Proto '05 (986 hp)
- Nissan GT-R SpecV '09 (1074 hp)
- Pagani Huayra '11 (1247 hp)
- Pagani Huayra '13 (1232 hp)
- Pagani Zonda C12 '00 (871 hp)
- Pagani Zonda C12S '00 (1030 hp)
- Pagani Zonda C12S 7.3 '02 (1035 hp)
- RUF CTR "Yellow Bird" '87
- RUF CTR2 '96 (961 hp)
- Saleen S7 '02 (942 hp)
- Shelby Series One Super Charged '03 (694 hp)
- SRT Viper GTS '99 (1095 hp)
- SRT Viper GTS '13 (1087 hp)
- SRT Viper GTS 15th anniversary (1031 hp)
- SRT Viper GTS R Concept '00 (1128 hp)
- SRT Viper SRT10 ACR '08 (1125 hp)
- SRT Viper SRT10 Coupe '06 (1159 hp)
- Tommykaira ZZII '00 (962 hp)
- Toyota Supra RZ '97 (937 hp)
- Volkswagen W12 Nardo '01 (920 hp)