Thanks to everyone for the timely and useful advice!!! I've downloaded the Mountain Guide and am looking at milebymile, Trip Wizard, and more closely at Google Maps. All these help.
To answer some questions... I've been afraid of heights all my life though until now I've managed it pretty well. Like bigjim, my fear seems to be growing with age. I only bought my 38 foot class A motorhome a few months ago. It's the first vehicle I've owned bigger than a car and this is our first big trip. We don't have any towing gear yet so my wife is following me in the SUV.
Stupidly, I planned 3 weeks in Oregon and Northern California zigzagging across the Coastal Range, Cascades and Sierra Nevadas. And I've been unpleasantly surprised by how much driving the RV triggers my fear of heights. Instead of gaining confidence with every mountain pass I successfully navigate, the discomfort and stress seems just seems to accumulate.
So, somewhat weirdly, I'm now more nervous driving the car on mountain roads than I used to be. I feel like I've surpassed my mountain road quota but still have to drive north out of South Lake Tahoe and eventually west over the Cascades again. I'll get it done but won't enjoy it. But, with your help, maybe I can figure out a route that doesn't cause my cortisol level to skyrocket. Thanks again all!
Zulu - the pic you shared gives me nightmares!