Just to weigh in a little on the GVW and licensing/insurance requirements. I'm going through this right now for different reasons in Colorado, and as someone mentioned, each state is a little different. So, my situation was my 2012 Ram 2500 was always overloaded, by like 1000 - 1500 lbs and it had a 9400 lb GVWR. Part of that is because Ram diesels are very heavy empty when compared to others. So I've been on the search for something that would work for my business and not make the business unprofitable at the same time.
In Colorado you are supposed to run DOT numbers on any vehicle over 10,001 lbs GVWR OR GCWR. You do not have to stop at Ports of Entry (The Scales) but you do have to stop at temporary inspection stations that are set up randomly - sometimes with portable scales and sometimes just a safety inspection. You need a CDL to drive anything GVWR or GCWR over 26,001 lbs and must stop at all scales/port of entry. All of the above only applies if you are operating commercially. If you have an F550 with a towing bed to haul your horses or some other similar situation you are exempt.
That's the drivers license and operation part. Registration is different. Any truck is 16,000 lbs or under is considered a light truck, and then they go class 4, class 5 and so on up to class 8 semis. Now, among light trucks there are 3 designations - truck, which can be used with no restrictions; Rec Truck, which is only supposed to be used for personal recreational transportation; and Farm Truck, which technically can only be used for transporting goods to market and transportation of goods between farm properties. In practice most people register with the least costly option they think they can get away with. For example if you have Farm plates you are exempt from Emission testing - there are a few places that require that here, particularly with diesels. Currently I don't see any police departments actively enforcing these rules so most people I know run Farm tags. I used to run Rec tags on my old Ford - even after I went back into business, and never had an issue. But that could change at any time so now I run regular truck tags just so I'm covered legally and liability wise.
Insurance isn't an issue for me as I run a commercial policy due to my business. But I don't think it's an issue here anyway. I see plenty of older medium duty and even semi tractors towing large horse trailers with farm plates and "not for hire" on the side. I can't imagine those people are paying commercial rates as they really sky rocket once you get out of the light truck category.
All of this would apply to box trucks also as in Colorado trucks are trucks and body style is not relevant. I'm not sure if any of this helps in your search. I have a feeling you need to decide what will ultimately be your State of residence, and then search their requirements. I would probably do that before even looking at vehicles beyond the normal vans or pickups as it may be a nonissue in one state, and a huge insurmountable mess in a state next door.