There is no way to legalize it, period. State "legal" means illegal. These are federal laws in your way, do not pass go, do not collect Skyline or pass go, pay money and have government collect your Skyline.
You are probably going to do it anyway, but just realize you are breaking the law. Not a little, not kinda, not according to certain points of view, 100% breaking it. You may go for a month or two, you may go for years, but you will always, ALWAYS be one curious government official away from getting the shell and any money and time you have sunk into it crushed. No ifs and or buts.
This car was once the property of a guy who thought he was clever.
This car was a former Motorex car that had not completed the legalization mods before the company failed and it had arguably the most knowledgeable guy on the subject fighting for its life and it still got executed.
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Make your choice.