If I were you, I’d start at square one… how are you going to get the car to the US? Find a shipping company that specializes in transporting automobiles, and I bet they’ve got someone who can tell you everything you need to know about tarriffs, inspections and such.
Plan on having them deliver the car to your garage, 'cause you won’t be able to drive it legally until it’s been inspected, registered and licensed. Forget about the road trip.
The second place you should call is your DMV. Ask them what it’ll take to get your car registered and licensed. See if you can’t get, on paper, a list of requirements / regulations that they’ll use when inspecting your car. This should come in handy when you talk to a mechanic.
That is, if you’re planning on driving the car on open roads. If you’re only driving your car on a track, then you’ve got a lot less to worry about…
If mods are required (depends on emission laws) you might be up against a HUGE amount of work, depending on the year, make and model. Newer cars are largely computer-controlled, and any sort of work that involves messing with flow rates, mixtures, timing, etc. can be very expensive to perform, and finding replacement / aftermarket parts can be a real headache.
I’d also try calling an auto shop that does work on racing vehicles and/or collector cars. They likely have the most experience with engine modding and might even know what it would take to get your import up to snuff.
Come to think of it… the mechanics would be the first people I’d call. They might be able to refer you to someone who’s imported a car. You should really find out how much money you’ll need to spend getting the car to pass inspection. That could be significant, compared to the cost of the car.
As a rule of thumb, plan on spending 2-3x the cost of the car in tarriffs, taxes, shipping costs, modification and registration. You got that kinda cash floating around?