If the Mammoth Lakes chamber of commerce and tourism department are encouraging 4WD backcountry driving, you can be certain that any stock high-clearance 4WD can handle the trails with aplomb. There'd be too much liability if people took their stock 4x4's out and continuously got them stuck on trails advertised in official literatature. I'd wager that even a RAV4 could drive on the trails they're mentioning.