Have you looked at the Frankenpony stereo camera? <http://home.comcast.net/~workshops/frankenpony/frankenpony1.html> I made one and used a double cable from a Pentax setup and it is not exact. The hinged release on the Frankenpony looks like it could be adjusted to get it close. I haven't built that part yet, I still am trying to get the old pony shutters to work well. I started on a MF stereo using Argus 75 lens and shutters but they as bad as the pony so I am still looking for the right ones. I do have a 4x5 stereo pinhole that works great.