California has an odd yet definitive line between what's registered as a car and what's considered a truck.
Every Bronco I know of, especially if they have original plates, is registered with typical car plates. But in an early magazine road test of a half-cab, it's shown with California black-and-yellow commercial plates. The DMV probably considered half-cabs to be pickups.
The same goes for El Caminos and Rancheros. I suppose there could have been exceptions, but they all got commercial plates when new.
Ford E-Series van with seats and windows: car plates. Ford E-Series van with no windows: commercial plates. (Of course, shuttle vans for hire would be the exception in that example.)
That makes sense. When I first registered my out of state 73 Bronco here in CA the inspector was unsure which it should be, since the bed was open. I explained that it was a wagon model that was missing a lot of parts, & originally the bed came with a roof over it. He called the supervisor over, who immediately said it was a passenger vehicle, without having to hear any explanation from me. He made my day.
My dad had a 37 Chevy pickup that he was able to convert to passenger vehicle tags. It was a toy for him & he never used for hauling. He had to take it to have it weighed, & it had to be under a certain weight. As he understood it, if he was caught using it for commercial purposes, it would be an expensive fine.
I had an old 70 E350 Club Wagon window van that fit the norm with its passenger plates. It seemed odd at the time, since it was heavy duty underneath, but the wagon designation was definitely a money saver.