[Buzz]

The Kirkhams own(ed?) an original CSX3--- Cobra roadster, and I'm pretty sure that was the initial baseline for their bodies, albeit with some tweaks and adjustments to correct the original's hand-formed imperfections and inconsistencies.
I might be wrong on this, but I seem to recall that their original Cobra started life as a street roadster and they needed to perform the requisite modifications to their tooling to produce their signature SC-style replica. I'm sure as the product evolved they developed the ability to produce any original (or other - like the flip top) body style that a customer preferred.