While I understand each state has their rules, DOT specifies only DOT belts to be street legal in the US. And then there is the airbag which is required to be removed per rally rules yet again the DOT requires the airbags be installed and operable. Don't forget federal emissions laws that require the OEM emissions equipment remain installed. Not sure who's law trumps who but, the feds usually have the upper hand. Also, most rally tires have on raised letters for competition use only not DOT approved.
Face it guys, very few if any performance rally cars are street legal in the United States. Most authorities don't have a problem but, come up with one who does, you are driving on the street with a car that isn't legal.
No, Federal law covers the entire US. Since at rallies, police know about the rally and leave us alone but, they could make trouble if they want. Most risk is driving the car not on a rally or having an accident with a civilian on a Transit where the cop could cause issues if he or she wants to. Not sure what you mean by highway patrol or police as highway patrol are police and they all have the responsibility to follow the law. It's really like bringing a foreign car into the US. Doesn't matter where you drive it, you have to get the import approved by someone in the Federal Government and they rule over the locals.