Not disagreeing w/p-Bar, and unsure of title--for personal, for commercial, new, used, etc.? CA automatically defaults any pickup to commercial use unless it has a camper permanently attached so I imagine 4500/5500 are the same. IIRC something you can't register is a pre-2007 medium-duty in CA for business use unless it has a 2007-or-later engine package (including after treatment). But on Ram's build-and-price today for two CA zip codes it shows a diesel is either standard or optional for most 2024 4500/5500, although you can't get one in a 4500 SLT. I know Ram's done some weird things but I'd be really surprised if they were selling trucks in a state (especially near the coast) where you couldn't register it.