I just did it here in Orange Co, CA last January. All I had was an engine and frame and a bill of sale.
First you need to run the VIN past the CHP. They have a more extensive DB than the DMV according to them. I actually was able to do that over the phone. Once I knew it was not stolen and no back fees, I built the bike and then back to the CHP for the inspection. Didn't even have to turn it on or check lights or anything. They then gave me a temp permit that I took to the DMV to get it registered and titled in my name. There are some DMV foms to fill out on their web site and take all the CHP paperwork to the DMV and you'll be fine. But see first if the CHP will verify the VIN over the phone before you do anything. Just tell them you're buying a non titled bike and want to be sure it's not stolen - good luck.