The vent wasn't standard on many cars. I think the early GT and GTI's came with the 10-speaker set up (not the 6 you get now) and that included the big one above the centre of the dash. The scroll on the front of it is for a vent, but it comes up at the front, right next to the windscreen.
I have an early ('54 plate) GT which came with all the pre-cost cutting goodies: metal glovebox handle, no roof aerial and a ten speaker system. Will try and get pictures up tomorrow in the daylight.
Nice colour car mate, glad to see your treating her well. :-)