Alex,
Jens raced the 2V some years ago, because he got sponsored by the german Guzzi distributor, they told him: we don't sell 4V engines, so you should drive 2V engine.
The question where to start? Depends on where you want to end:-) And the money. Decide what the endgoal should be, then start buying accident bikes that have the right parts, sell what you don't need, that makes it a lot cheaper. 2 years ago I bought a v11 le mans, took what I needed, and sold the rest. I earned money on that deal, the parts were free to me in the end! After that was done, I started swapping pieces against more expensive ones. That's not for free:-( The bike is finished in that. I will still be changing things, but more to clean up things.
Next is a new tank, with build in pump& filter.
Mounting the moto spezial ecu with new wireloop.