Yes, they built the Cobra for Shelby. The first Cobras were basically an AC Ace with a Ford Fairland V8 and only a few changes (Jaguar differential rather than AC differential, to handle the extra power, etc).
I imagine it is an AC Ace converted by an owner to have a V8 like the cobra. But it could be a very early AC Cobra: The AC Ace had the gas filler on the side, like this one does, and except for the first few Cobras made, the gas filler on all Cobras was in the middle of the rear deck, not on the side. If this is one of those first first it is worth several millions and came originally with the small (260 cubic inch) engine. Someone has done a very neat job of slipping a much more modern Ford V8 and those gorgeous Webers in, and a thicker radiator too. Lovely car.