You build your Cobra how you want to build it.
There's me with a 302 Windsor and a modern preformed dash and Honda seats (very comfortable)
There is no point going down the I want it original road as you'll simply never get there.
My attitude is does it look like a Cobra and if it does your almost there.
These GM motors do seem to have advantages over most, but at the end of the day its up to you and what your budget allows.
At the end of the day - these are FUN cars that will raise a smile every time you bring it out of the garage.
One thing for sure, if you do go ahead there are plenty of helpers on this site who will come to your aid.
Whether its Fabricator Mike, Sander Les, Lexus guru Scotty, HP Craig (and add Garrett) or burger man Bern you'll certainly have fun using the site.
Oh, and if you want a set of neons - I'm your man