If your building one from scratch then id but as good as condition shell as possible. Na or turbo doesnt matter. Get the shell shot blasted, any rust removed and repaired then fully protected.
These cars are getting on now so it wilk be next to impossible to find one with no rust.
Brakes rev 2 onwards are what you want- na and turbo are the same.
If your going to the hassle of building a 2gr then buy the gearbox seperate anyway. The money you save buying a na and a turbo will prob be enough for the decent gearbox as paul has mentioned