Quick update after a few months of fighting with the DMV and ARB: I have been told repeatedly by representatives from both organizations that there is a no-exceptions ban on registering so-called "direct import" vehicles unless they go through ARB's testing and compliance procedures. This is assuming your vehicle doesn't have an EPA Certificate of Compliance (it almost definitely doesn't, and EPA Form 3520 doesn't count as a conforming document) or the Toyota Letter (I spoke with a rep from Toyota of North America in Plano, TX and they don't issue the Letter anymore. To anyone. Ever. Not sure if they ever did.)
So, assuming you don't have those two unobtainable documents, you have to drop your truck off at California Environmental Engineering in Santa Ana and having them run it on their FTP (federal testing procedure) dyno setup. They are the only company licensed by the ARB to run these tests, and apparently it's about $1,500/hour. After that, they tell you what "repairs" need to happen (i.e. what you need to have installed, refurbished, etc.) to meet ARB's emissions thresholds, which are just U.S. EPA standards that California enforces as a matter of state law to undercut the 21-year EPA exemption. I haven't gotten an exact dollar amount for this, but it's easily thousands of dollars (think new OEM cat, new OEM injectors, rebuilt injector pump, full engine rebuild, etc.). Again, they're the only business in CA that ARB works with, so they can essentially write their own paycheck. This process takes "up to several months," according to the company.
I would STRONGLY encourage you to be careful before bringing in any out-of-country truck to CA. The DMV will not listen to you, nor will ARB, no matter how special or unique your situation is. I brought my '85 Surf here after visiting the CA DMV's website and seeing, in plain English, language that said I could register it here no problem. I got here and they refused. I bought a cheap Civic to get to work while I sorted everything out. Well, the Civic got burned up in the north bay fires, along with my house and all my stuff except the Surf, which started right up and let me roll my ass out of the neighborhood while my in-laws crept around fallen tree branches in their Tesla (no disrespect to teslas, they're pretty cool to be honest). I wrote a letter to the DMV explaining the situation, and included screenshots of the misleading language on their website. They didn't care. They didn't admit fault, nor were they willing to acknowledge the hardship they had created (or the thousands of dollars I had spent due to their mistake). Didn't care in the slightest. I'm only telling you this so that you don't fall into the same nightmare situation I did. Please just be careful. CA is a beautiful state run by well-meaning idiots.