I am really interested with CT engineering intake, but I can only find this intake on ebay and the seller is apparently from US, and I wonder if it is going to fit to non-USDM S2000 because I live in Australia.
Also, is it going to fit with aftermarket radiators? because I am sure that the old owner had installed aftermarket koyo radiator.

 

Maybe try contacting CT engineering directly or contact one of the vendors on here like THmotorsports. They can probably help you out with ordering it. As for fitting with the aftermarket rad I am not sure.

 

The thicker radiator pushes the fans out into the area where the intake box would go. However I'm sure if you don't mind defacing part of the box, you could notch it out to accommodate. That end is already open/exposed to draw in air. I think removing about 1" more would be enough for the box to slip by the fan housing.