Some suggestions:
Painted Rock Petroglyph site & campground - 33.02287, -113.04959
Organ Pipe as Steve suggested
Wupatki Pueblo ruins National Monument - boondock area: 35.52773, -111.43741
Death Valley National Park has more than a lifetime of exploring available
Cathedral Gorge state park in Nevada
Do get a benchmark road and recreation atlas for each State. Shows landownership, making it easier to figure out where to boondock.
If the winter is stormier than you like, an alternative to 395 is to get to Prineville either over Government Camp or from Hood River, then to Burns on hwy 20, then Winnemucca, then south either through Fallon or Austin, depending on road conditions. From Tonapah on south should be clear sailing.
Have fun
35.52773, -111.43741