The laws here are silly. More than a 5% hp increase, and you have to take the car to our version of the dmv and have it checked out and approved. You rarely get it approved if you dont have papers from the car manufactorer that the car can take the power. Ofc you build have to be solid as well, but that is a good thing. Nissan in Norway refuses to guarrantee anything. Which makes it hard to do stuff to datsuns/nissans. While the volvo guys can get chevy engines approved, because volvo gives you papers saying everything is good :P You also have to get the car approved if you have rims that are in the wrong size. Like my old nx2000 had 15 and 16" in its papers. I wasnt allowed to use my 17" rims.
So with a datsun; if the car didnt come with the engine as an option from the factory, getting it approved is hard. Usually easier to tune the engine that came with the car, and get that approved.
We cant get skylines registered for street use here either, because they havent been crash tested by the correct european company. Norway doesnt accept tests from Asia. But Norway love TUV from Germany. So if you modify your car, and drive it down there and have them approve it. You have a big chance of getting it approved here as well.