After driving Sonora Pass a couple of times in my truck, I contacted the Highway Patrol office responsible for that area. I spoke to a female officer. I told her that I had a six cylinder four liter Tacoma with a 6000 pound rating towing a 12 foot trailer weighing 2000 pounds and would be coming up from the east side.
She said it was doable. I did it. No problem. I would NOT do that pass in anything longer than 20 feet. We spent a week boondocking near the pass and saw two accidents involving over-length vehicles that could not stay in their lanes. There are several hairpin turns.
And coming down, I put it in low gear and rode the engine compression all the way down. There are pull-outs if you need to let faster folks go by.
PS -- if you go into the back country of Sonora Pass with your truck scouting for off pavement boondocking sites, make sure you have great tires. We had BFG Rugged Trails and the volcanic rock sliced one of my tires. My wife learned a few new words as I changed the tire at ten thousand feet. She also learned how to use a torque wrench.
When I got home, I switched to BFG All Terrains. No flats since then!