There are no firm published figures on imports from anybody, which makes things different.
They don't really follow the standard trends of other vehicles, which is why it's so difficult.
A non-turbo will sell, as there is a market for it - those that want the advanced features of a mid-90's skyline that costs no more than that for any locally sold model.. A series2 non-turbo however could be asking for trouble.. especially if you are asking up towards $20k..
I know most would think "well i can get a very well modified Series1 for $18k, why spend $20k for non-turbo, even if it is series2). I think you'd probably get burnt at resale.
Depends what you are after, if its a tax right-off, then go for it