Since Aimless mentioned public transit to Yosemite, how about a lollipop hike with the John Muir Trail out of Yosemite connecting to the Big SEKI loop? That seems pretty close to the mileage you are looking for. Here is info on the Big SEKI loop: https://backpackinglight.com/forums/topic/73686/

Some words of caution: hiking in the Sierra is probably unlike anything you have done before. Miles there contain significant elevation changes. To do high mileage you need to be in very good shape and have a very light kit. Resupplying on the PCT is not easy. The trail does not go through towns. You typically have to hike over a pass to a trailhead and then hitchhike (or walk) to a town and then reverse it to get back onto the trail.