I'm surprised showhauler even built that unit a 46', 45' RV length has been a national standard for years. Should not really bother you though, only 2 places length is automatically checked, some scalehouses have a laser that checks that at the same time they weigh you, but I suspect you are not crossing scales. Also, they can do the same thing at some turnpike toll booths, but those personnel aren't dot cops so you should have no problem there either. I know for sure that the WV turnpike checks width and length automatically, I know someone who was towing an overwidth sailboat and got the redlight at the toll booth and had to backtrack and find a way around the whole state...
Most states now have 72' max, but some still have the old 65', either way you are way over. In the past, race rigs like that have pretty much gotten a free pass when licensed as an RV but that is all changing as the states are hard up for money. Some states are actively targeting racers, defining you as a commercial vehicle with the theory being you race for a purse so it is for profit. Also, racers are an easy target for overweight tickets, most of the smaller trailers are overloaded as soon as you put in a racecar and some tools, add a atv or golf cart and you are way over. I know a local dirt racer who had to pare down everything in the trailer, go with a smaller atv and really be careful to get the weight down to what the trailer was rated after an expensive ticket. Check out some of the forums on
Old Hippie, they have a bunch of racers posting on there. The guy that runs the forum is selling a similar rig that was way to long and going to something smaller.