Ant has a point there, it's apples and pears really... If you'd spend a few 100K building whatever race car, it might be quicker than anything else on the track, but to what expense, and furthermore, will it still be road legal?
If the topic opener wants to know if it's possible to build a road legal Cobra that will keep up with other cars like a Z06 or Exige, yes it's possible. Will there be faster cars around the track? More than likely...
I've done lots of trackdays in the past, and i'd suggest to get something with similar performance to your buddies, so you can keep up, have lots of fun, and learn. Because that's what a trackday is all about
