I drove that Highway 58 eons ago back in College, but not much is remembered from those times.
When a Storm was about to pound SoCal last December, that Highway was given on Radio as a alt. route for all Traffic.
I've become a big fan of flyover pix on Google Earth for Trip recon. Once downloaded, you can invoke left side Website page options like Reviews of places [on TripAdvisor], and uploaded Tourista pix on 'Panoramio'. I scouted in advance a Boondocking trip to Lake Powell. It was very kewl to see so much in advance. There were plenty of linked Big Rig Owner Reviews re: various Campgrounds; view spots; and Fuel Stations. If Google Earth isn't working for you on your 'Net connection speed, at least try Trip Advisor for Reviews. Since you're heading towards where ~80% of U.S. Fruit/Veggies come from, perhaps Semi Truck Haulers you chat up can tell you about Road conditions. If there's some restriction re: ' 30' And Over To Kingpin Not Advised ', that info would be on the CalTrans Website. I don't believe that's the case.
My main point here is that a lil readout at the Google Earth Webpage bottom tells you ground elevation at the crosshairs icon. Along with a scale, as on a Map, you can deduce over linear distance how steep grades and curves are, and other info that prevents being blindsided like Ricky & Lucy in 'The Long Long Trailer'.
I zoomed in on the Campground at 'Lee's Ferry' AZ to see fine details in advance. Very kewl.