4. Make sure it doesn't "technically" count as a car
Obviously this is financially prohibitive, but for the sake of argument, say you had the kind of funding to do a complex project car. You could, in theory, strip the car down and bring in just the parts that the government doesn't care about. Removing the engine, transmission, wheels and tires, seat belts, brake hoses, and the like will result in the car being counted as parts. Put U.S.-legal versions of those parts on the car (i.e. buy the parts here), register it in your state as a custom vehicle, and you're all set.
Aaron Miller is the Rides editor for Supercompressor, and can be found on Twitter. He would definitely drive a Holden or Vauxhall Maloo in the States just for the novelty of it.