I've been into the Dollhouse twice with my set-up. Not a full size, but I certainly believe a full size with good ground clearance & tires will do just fine. There are a few tight turns that will require patience and finesse, but totally doable.
That said, even having gone in twice, I would still prefer to travel with at least one other vehicle. Heaven forbid something happen to you (not just the truck, but you personally) it could be a long wait for help to arrive. The Dollhouse is incredibly remote and challenging terrain, especially when in distress. But it's really worth it if all goes well!
Horseshoe Canyon, the part you can drive to, is a breeze. Just a lot of washboards, but I never even put it in 4WD... a Honda Civic could make it to the trailhead just fine. Great hike down to the petroglyphs!
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