The show "Top Gear" keeps a list of all the cars they have featured/raced and the track times each one achieved using their closed course and driver. I'm not sure if they have ever featured the Cobra and the associated track time. This might be another source to answer this question. Well...I just checked their web site and they do not appear to have run a Cobra. The link to their list is included below. I guess someone could speculate when an original car (or your car) falls in the pecking-order.
http://www.topgear.com/us/assets/tracktimes.html