I actually just restored a 1978 Suzuki DR370 and I was looking to get it registered. I had found it on the corner with a "for free" sign on it. I never ended up doin because I couldn't find a straight answer from anywhere I checked. I've heard that some people say that they created the bike from scratch and that when they got it it was just a frame with an engine. Or that you can file for a lost title. OR there is another option where its somethin along the lines of an "abandoned vehicle" re-registration... I'm not sure on any of this information but its what I gathered from scowering the DMV site and all kinds of other internet based forums and information sites. I'd like to find out more about the abandoned vehicle registration and that might be your best bet if theres a process for that.
My toys:
'84 T3 red Parts bike
'84 T3 green (runner)
'85 Tecate with an LT250r in it
'04 Kawasaki KX250F
Don't blame the ride, blame the skill.