Well, obviously the X2011...but that is irrelevant for most races. We need to know if there are any limitations on power/weight. You could beat any viper or ZZII with the x1 or f1...so I'm not sure how to help with your question.
GTRs are nooblet cars. My favourite drag categories are probably the 9.9 class-Supra Vs RX7 Vs Mustang Vs SVT Cobra, or the 9.3 class-R34 Vs Z06 Vs ZR1.
As you're new here, I'll ask have you seen the Drag Racing Sub-Forum? Like this is the Questions and answers sub-forum, so just look at the very top, and in the train, choose "Gran Turismo 5, and look a bit farther down the list of Sub forums and you'll see all the drag info you can handle 👍 And welcome!