I did some checking on my end and can offer up some tidbits -
They only had a couple of the Nikkor lenses at their disposal. There is one scene where the camera pans around the room and, in the same shot, you can see two HAL interfaces. Apart from that, they just moved a lens from set to set.
All of the HAL interfaces were the same size. Different ratios and layouts were experimented with, but eventually they settled on the long slender layout seen in the Pod Bay and Centrifuge set.
The short/stubby HAL interface that was discussed here, though made for the film, was not ultimately used. It was a prototype of sorts, but the proportions changed down the road. Story goes it was discovered in a junk shop (or would that be 'shoppe') in London along with the Brain Room key (which is screen used) after filming. It followed the same construction techniques, has an original decal, but is not the actual (final) size. Also, the screen is probably not original.
I suspect that since there were multiple interfaces and only a couple of lenses that the interfaces had some sort of mounting ring that was a copy of the mounting ring from a Nikon camera body for the lens to securely mount to. The short/stubby interface posted here doesn't seem to have anything more than a beveled ring.
The HAL 9000 decal is a decal. Not some sort of plate that was affixed. White outlines on blue/black. (Though I have to admit I wouldn't mind an aluminum plate with the lines in the bare aluminum.
13" - 15" high with corresponding proportional width "sounds about right".
So, with that being said I've always thought that the plan of attack should be to find a decent lens that is the approximate shape and size and build the interface around that - keeping the proportions the same as what we see on screen. That way, it will "look the part", even if it isn't made of OEM parts (so to speak). I will call around some camera guys I know and see if I can get 15minutes alone with a real Nikkor lens.......
Like I said, I would be up for getting a bunch of those little HAL 9000 labels made. Surely we could do some sort of printing on a stamped metal plaque?
Gene