Bogdan,
just an FYI, its not really gonna be feasible to try and focus the camera. There isn't any rangefinder that is calibrated to a lens, similar to the old "press" cameras such as the Graflex, etc...
Now, if you intend on shooting it like a p+s, fixed focus at say, infinity, then you'll just focus the lens on the g/g, lock the focus, and if you can find a suitable v/f(I don't know of one off hand) that matches your chosen lens' field of view, then you can go to town
.
But if you try to focus the camera handheld, I believe you'll end up with a bunch of out of focus, blurry sheets/rolls of film.
-Dan