Mt. Diablo for sure. That's my bay area "Training Mountain" for most big hikes these days. 5 times already this year.
I'm planning on a overnight camping trip with two full Diablo summit climbs before my Whitney attempt. Basically, that's a good approximation of the elevation gain, plus an overnight stay.
As for elevation, Mt Lassen is a good hike to see if you're likely to be affected by the altitude. Even if it's only to 10,000 feet it's a good test.
Some time in Yosemite climbing the Yosemite Falls trail or climbing up to Glacier point via 4-mile or Panoramic trail would be good, or Half dome.
