The magic formula you need is rear node-to-film distance = f*(1 +m). f = lens' focal length, m = magnification, and for most LF lenses the rear node isn't far from the diaphragm.
Originally Posted by Buster6X6
Either camera will work well if you're shooting straight ahead. The Toyo probably offers more flexibility.
Which lens to use? Can't answer with the limited information you've provided. What have you got (make & model as well as focal length)? What magnification do you want to shoot at?
About exposure. GN arithmetic will give you the effective aperture you want. GN/(flash-to-subject distance) is it. The GN of two identical flashes = sqrt(2)*a single flash's GN. To convert effective aperture to the aperture setting to use, aperture set = effective aperture/(1 + lens' pupillary magnification*m). For most LF lenses, pupillary magnification = 1.