I believe Cambo called it a tripod block. Sinar calls it a rail clamp.

For a lens I would look for something from Schneider, Rodenstock, Nikon, Fujinon or Caltar in a modern Copal shutter. Since you are doing architecture I would look for a lens with a large image circle.

Why 135mm? A 150mm can give you more room for movements and is very similar in focal length.