Car camping in N. California with access to alpine landscapes

[Love the Sierra]

I agree with WD and all of the others. Here are a few more ideas.
On the EAST side of the 395, just past mono lake on the 120, is a wonderful, big forest, great for dispersed car camping. It makes a great spot for all sorts of wonderful day trips up the Tioga Pass. You can easily drive into Yosemite, or go to TH for Saddlebag Lake, Dana Plateau, or TH around Bridgeport like Barney Lake or Virginia Lake.