I've used the blood type information for over 10 years now. The keys are to be aware of body pH and your parents blood types. You'll notice people posting against the diet never put up the pH/parent information. :)
As for correct beans for natto, I'd check wildfermentation.com as a possible source. Not sure if they cover it, but the process is a bacterial fermentation. I guess you could try lentils and peanuts yourself, not sure.