Stick with an Eaton type supercharger (as fitted to the Mini Cooper and SLK), this is a slim-line twin-rotor (essentially a Rootes type) supercharger which will fit nicely into the 'V' of your Cologne, and can be seriously over-driven to make power.
4-71, 6-71, 8-71 etc are too tall to fit under your bonnet.
Centrifugal superchargers (like the ortech or Paxton) are easy enough to fit, but a kit will run out at about £3K unless you can find a second-hand one.
'Blown' simply refers to an engine that is supercharged - Blower = slang term for a supercharger.
Good luck