Thought I would throw in a view from across the pond as this seems to be mainly a discussion on the US side.
Firstly, whilst I believe that the best place for the engine to be located in any supercar is midengined, I think it is shortsighted to believe that you cannot have a supercar unless it is midengined (e.g. 911GT2, 911 Turbo, 550 Maranello, Aston Martin Vanquish to name but a few).
On the subject of the Z06 or the GT40, I think it is very difficult to compare the two animals as they are such different beasts. I personally am a fan of Porsche road cars and am on my third one at present. However, whilst these are undoubtedly great performance cars, they just do not excite like a GT40 - so I have a GTD40 for times when I want something different and to get the heart pumping.
Now I live in London where just about every supercar are seen all the time (even Lamorghinis and Astons) and usually do not get a second glance. However, even when my GTD40 is just parked up in the drive outside my house, it literally stops passing traffic, with people getting it out and checking it over. Similarly, when on road (either being driven or on its trailer), I have to be careful because of the amount of cars buzzing around it with their drivers grinning from ear to ear. You have to see it to really believe it!
I have always wanted to own a GT40 and I wanted to do it whilst I was still young enough to enjoy it. I plan to compete with her this season and am very glad that I made the decision to buy one last year (I do not have the time or expertise to build one myself).
The only other car I would love to own as much as the GT40 would be a replica (original if I could afford it) of a Porsche 917K which took over from the GT40 after the famous Wyer GT40 victories in 68 and 69. However, unlike the GT40 replicas which are built extremely well, the 917 replicas I have seen are typical kit car rubbish (please let me know if anyone knows any decent ones).
Just my two penneth worth!
Martin