First rule when registering a car in Sweden are that the vehicle must be in a series manufactured state, which actually means that the car should be in the same state as when it left the factory where it was fabricated. Please take notice, this is what the book says, and more often than not there are serious disrepancies between what the book say and how reality is.
Going for a bone stock car would considerably reduce the risks of running into an awful lot of problems which seldom takes little work, effort or even money to solve. If you receive a remark on non-stock parts on your car when you attempt to register it, the Swedish DVLA may very well demand that you make a stock component comparison, and that would be a hard and time-consuming task at the very best.
Just like Yakozan said, you would be far better off buying a car already registered in Sweden if you want to buy a complete package and not do the tuning yourself.
When importing a car directly from Japan the authorities will probably demand certificates on brakes and bobbery unless it's a car model already sold in Sweden as a new vehicle during its production run.
In addition, once again like Yakozan pointed out, the currency fluctuations of late would considerably have reduced the expenditure cuts you could otherwise have made by importing a car directly from Japan instead of selecting an object already within the EU in general and perhaps the UK in particular.
There's a good market for the cars you mentioned in the UK, the economy crash has hit them there as well and a good deal of people seem compelled to sell their cars in order to cut expenditures, just like they do over here, and you may very well say that it's a buyer's market at the moment.
Moreover, cars imported from a EU country will, as opposed to importing from a third part country, most probably render you much less problems during registration. If you then register the car as an import for private use (limited to one car per person in a twelve-months period) you will probably only have to show a certificate from the manufacturer or their agent-general that the car model is manufactured as part of a series - unless, of course, the model has been sold as a new car within Sweden.
As Yakozan very aptly remarked, the process of importing a car could be either heaven or hell.
00-02: BMW/Alpina B7 Turbo '80 - 05-06: Nissan Skyline R33 GTR '95 - 06-XX: Nissan Skyline R34 GTR '99
09-09: Ford Sierra Cosworth 4x4 '92 - 09-11: BMW/Alpina B10 V8 '97 - 11-xx: Maserati 3200 GT '99
Commodum Habitus Ex