The campgrounds near Tioga Pass are not reservable and fill up quickly. If you relentlessly check the Tuolumne Meadows (Yosemite) campground availability on recreation.gov, chances are you'll see a cancellation eventually and can snap it up. But I mean relentlessly, particularly in the last 2 weeks before your trip, several times a day. I've never lost out this way. TM is 9,000', so good acclimatization for you on the way to Tioga Pass.
