There was an East German stereo camera made by Belca called the Belplasca which had twin 40mm tessars. It was a scale focusing, not rangefinder camera. It is a fine stereo camera, somewhat expensive due to it's rarity. I have one.
I also have a bracket on which I can mount 2 identical cameras and fire them simultaneously with a twin cable release. The only reasons to do this instead of a regular stereo camera is to vary the stereo base (distance between lenses) and if you have interchangeable lenses, you can try stereo with wide angle or telephoto lenses. This setup is very heavy and I rarely use it.
My preference is a stereo camera I can take everywhere with me; I always have one loaded in my car.
Incidentally, the Fed stereo camera and the above mentioned Belplasca both use a rectangular format. Unfortunately the Fed chooses the shutter speed for you as you pick the aperture. The Belplasca is totally manual, and has the better lenses. I prefer choosing my own shutter & apertures.
There's another Russian stereo camera called the Sputnik (I have that too) which uses 120 film. It has decent triplet lenses but is almost always afflicted with light leaks & internal flare.
In my opinion, if you really want to get into stereo photography, the best stereo cameras are a well-tuned Revere, Stereo Realist or Kodak Stereo; they are cheap to buy and because they were the most popular, many were made making spare parts easy to find; if you can get one, a well-tuned Belplasca is also worthwhile.
I have owned or used nearly every stereo camera made in the 1950's.
