Kevin,
I had the same question so I went to the DMV weigh station in Iowa where I reside and ask them, he was an old timer I would say pretty high up he had to look it up and told me I would be over length because we are licensed as a motor home 65 ft is the limit 70 ft if I were a pickup pulling a fifth wheel pulling a boat ? Which didn't make sense ???
So I ask him how all the Prevost go by with stacker trailers all the time and he said no one knows the actual Law he even had to look it up, he told me not to worry about it,
But you can bet everything you own if there were ever an accident the Lawyers would Know exactly what the law read and would tear you apart ,,
That being said I have a motorcycle lift on the back of my bus then the sterling tow bar then an unlimited Jeep Rubicon and with the spare tire on my jeep on the back I think I am around 73 ft long , I guess its a roll of the Dice !!!