Nice route from Marin to Sacramento?

I'm thinking of cycling from San Francisco to Sac'to in June, via Marin. The SF-Marin part is easy but can anyone offer suggestions for the rest of the route? I grew up in the Bay Area and remember that Hwy. 37 was sometimes called Blood Alley -- I don't know if it's even possible to cycle it, much less halfway safe. I don't mind a few hills but would prefer to stick to the flats, on lesser trafficked back roads when possible. But maybe that's asking the impossible.

My wife would probably pace me in the car and we'd stay at a hotel or two along the way -- no camping.

Thanks in advance for any help.