One of the rarest hardtops available for the Triumph Spitfire made by Lenham was not their fastback hardtops, of which 4 are known, but the "two piece" targa/surrey style hardtop named Torado. It is the only Hardtop, I have never seen one, not even a modern photograph.
The german company "Körbler" made targa styled hardtops for Fiat, Alfa Romeo as well as Triumph Spitfire MkIV and 1500 . There is information and pictures to be found here:(http://www.spitfire-forum.eu/viewtopic.php?t=6713 - in german).
The main difference to the Lenham Hardtop is the rear window and the way the hardtop reaches back. Although Lenham made the Hardtops for early Triumph Spitfire, they can maybe still used on the later MkIV and 1500 models.