There are some tunnels around Yosemite that are marked 10'-4" but that's vertical clearance at the curve. Being too conservative may make one miss out on some great routes.
My first reaction after measuring a large rented Class C was the same as on link -- to avoid the road. But once there I saw many larger RVs and buses getting through so I knew I'd be fine as long as I stayed close to middle.
Link has nice pictures of tunnels.
Hwy. 120 to and through Yosemite