In Wisconsin your truck and trailer with Farm plates you would still need to have a current CDL Class A to operate it legally. They also require the farm trucks here to have a yearly DOT inspection sticker on them and the Farm / Owner of the equipment is required to have a USDOT number. I know that its common for people getting a CDL license to use a ton truck and gooseneck trailer like yours to take the driving test. You might want to check with your insurance company and see what they feel is needed. I would recommend you contact the MO department of transportation and see what they have to say about your situation. I've had very good luck talking to the Wisconsin Department of Transportation over the years. I've been in the trucking business since 2003. Be safe and cover your bases. Don