Wayne, I have my 3x4 Crown in hand as I write this.
The boards are unique to this format - different from the 4x5 boards, and I think different from the 2x3 boards as well.
With the front standard stowed inside the body, flange-to-film is about 33mm. With the front standard pulled out just far enough to grab hold of the focusing bed, flange-to-film is about 58mm. With the front standard pulled far enough to just clear the body, and allow semi-reasonable finger access to the knobs that control front rise, flange-to-film is about 72mm.
Added later - as far as which lenses will fit, the front standard opening looks like it will swallow a maximum rear cell diameter around 55mm.