I've ridden Ozarks-Calif. numerous times, both east and west bound versions.
Think Eureka Springs as the jump off point west. From there you'll have to decide the more northern tack thru Colorada, or more Southern across Texas, NM and Az.
If it were me, I take the southern route west bound, and visit Monument Valley, and Grand Canyon. Pick up old route 66 in the Seligman, Kingman area into Calif and ride on west San Luis Obispo to pick up the Coast Highway. Just get out your atlas and find roads to connect those places.
Set aside one full day to make the ride from Big Sur to Bay Area. Not many miles but lots of beauty and good riding, do it justice by giving it the time to soak it all in.
I suggest turning east out of the Bay Area. If your plan is to keep riding north to Oregon on the Coast I'd revisit that. You can do it that way, but its ALOT of riding. The best is south, and you'll have to add more than a few days to the tour to work it in. You can't do it all on a single tour. My long term strategy on that would be a west tour next year using a high north route through Montana, and Washington then back south on 1 to San Luis.
Anyway I'd ride back east through Yoseminte, Tahoe and U.S. 50 across Neveda. I'd ride the mountains of Utah and Colorado working my way east. Many roads and ideas to do that, just pick. Once out of the mountains, I'd just work my way back to Ontario on routes that fit my mood on that day.
You're looking at 6,000 plus miles. Some fail to forget how much goes into a 2-3 week ride. It can be a blessing or endurance test. I find the latter to not be much fun. Many fall victim to the too ambitious trap. Linking a series of 600-700 mile days looks easy on paper. I strongly suggest varying the daily milegage. I might 5-600 miles 3 days in a row, and then throw in a 250 easy day to break the routine. After 6 days of riding I take the 7th off, or maybe the 8th, depends. On that day I don't ride. I spend the day washing my clothes, visiting friends, and enjoy where I'm at. On my cross country rides I took that day before heading back east.
It makes all the difference. I got back on the bike recharged and ready to ride.
The amount of riding and scenes out west can be overwhelming, guys tend to try to do too much, and wind up not seeing anything and not having a good time.
YMMV.