[Tengu]

G'day Chris, best of luck if you decide to build. As others have said, look around a fair bit before you settle on a choice. If you can get some drives in a few, even better. There are so many choices out there, I guess the first thought is what you want your cobra to be, a kit car with a wide variety of options, or a reproduction of the original with its inherent limitations. I chose old school and bought an American build, because I wanted an original but couldn't find one I liked for the right price. It drives like a 1960s roadster and I love it. But jump into a modern kit and some of them are awesome with performance and handling that is hard to ignore. If you go old school, BBF is the way to go, modern school, the sky's the limit. It's obvious from his forum that chev engines are a very good and acceptable choice, even Lexus (haven't heard of a Mazda rotary cobra yet, that would be interesting)
Instead of reinventing the wheel, find a cobra you really like and either buy it, or use that car as the basis for your project, rather that make it up as you go along.
I lack knowledge of Aus kits, but there is a wealth of knowledge on this forum, make sure you take up member's offers of advice. Don't think your question are stupid, we've all asked them at some stage. Oh..and research, research, research !!!