I didn't comment when the original poster asked what members thought about this truck he wants to buy but his first post mentioned that the truck was modified. I don't remember what mods it has, probably a magic black box.
I would not buy a modified used truck under any circumstances but particularly not a CA truck I was going to try to register in CA.
My advice would be to walk away from this truck and keep looking. A modifed truck could very well have been abused. HPCR injectors will not stand up well to increased rail pressure which black boxes often cause and if the buyer could be facing one or more injector failures not to mention the risk of a melted piston. Even one injector is expensive not to mention all six.
With careful and patient searching it is possible to find a clean low mileage unmolested Dodge-Cummins owned or previously owned by an old guy who left it as the factory built it, serviced it properly, and drove it with care.