If it's the career race you're talking about, the Toyota TS050's fuel lasts forever (ish), good brakes and modern aero makes for a strong choice and the hybrid system is very user friendly.
To answer your group c question, they're set up more for top speed rather than cornering so you'll scrub the tyres more plus they're less fuel efficient. Other than the difficult to turn Jag, they're all good fun but they're not as forgiving as their modern counterparts.
Gotta give an honourable mention to the '11 Audi R18, Pug 908 and the screaming Gr C 787B.
