I couldn't get the link to work (I'll try again later), so I did some more surfing and found that the car with the strange dorsal intake behind the 6C at Retromobile was in fact an experimental mid-engined Junior Zagato!!!
Called the Junior Z Periscopo for obvious reasons, it clearly predates the 6C and uses the Alfetta 2-litre engine (and presumably the wheels, which is why I thought it was a mid-mount GTV). Here's the linky, hope it works - there's a couple more pictures of 6C that I haven't seen on the following page, with the profile shot in particular suggesting an extended wheelbase necessary to fit the engine in-line rather than transversely???
ALFA ROMEO AlfaSud Sprint 6C : - Motorlegend.com
I love the idea of mid-engined Alfas, but until recently I had never heard of the 6C, let alone a middie Junior Zagato! I've often wondered whether the Montreal was intended to be mid-mount, as there are those huge vents on the B-pillars, and the OSI Scarabeo (allegedly using a precursor of the Tipo 33 H-tube chassis) showed how the Guilia twincam could be mounted sideways.
There is no way I could ever afford a T33 Stradale, let alone the one-off Carabo (my favourite derivative), but a middie-Montreal would have been a neat machine, even with a 4-cylinder engine...