As Jack stated, Florida will NOT allow you to register your tractor as a motorhome. Our Kenworth was a fully equipped (kitchen/ bathroom w/shower/ full sized bed, etc) tractor with 170" of living quarters exactly like a small Class C type motorhome inside. But as long as the fifth wheel (or a gooseneck) hitch was attached to the tractor and the intent was to pull a fifth wheel RV or gooseneck type of trailer, it could not be legally registered within Florida. Not to say that a person could not temporarily remove the hitch, register the tractor as a "motorhome" and then replace the hitch afterwards and then run illegally with it. For us, the risk were to great! I will scan and post the Florida documents pertaining to this given to us by DMV and which clearly define this restriction.
So, we currently run under a Florida registration which classifies our Volvo as a type "RMR" vehicle, and because we registered the GCVWR at less than 55K are not required to pay the Heavy Highway Use Tax which runs about $550.00/ year. Our annual plate (sticker) renewal will run slightly more than $300/year. If you find a better deal to legally register your tractor/toter, please share it as we too would be interested.
Someone put this here on this site but i haven't be able to contact him.
I don't know what RMR means and i look for it but nothing came up