If I were making that trip and had 3-4 weeks, I'd go over to the coast at Morro Bay and then up Rt 1 to San Fancisco. Cross the Golden Gate and take 101 to Cloverdale, Hwy 128 and then go up 128 to the coast. Stay on Rt 1 to Leggett, then north on 101 to the Redwoods.
A word of caution about this route. It's got a few narrow roads and there's a lot of curves, but the drive and scenery make it worth while. We have a 40' Marquis and did this route north forrm San Francisco last year with no trouble. I happen to enjoy this kind of drive, so the roads didn't bother me, however, some folks who have done the section north from Ft Bragg say "Never again, we must have been crazy to try it." I used to live in Half Moon Bay and have driven the coast Rt 1 to Morrow Bay many times and always enjoy it.
Chet18013