you can easily turbo either ...
having said that ...
for a basic setup you would need the turbo model's (either 34 or 33) manifold, turbo, intercooler and plumbing, ecu, fuel pump, injectors etc etc
even with all this the static compression ratio is alot higher in the NA models. This fact is a double edged sword. In one hand it provides better driveability (to an extent) but it will ultimately restrict the amount of boost and hence power that you can produce. You can push the factory turbo motor so much further for the same amount of money or less.
if you want a turbo skyline IMO it would be cheaper to buy one already turbo charged from factory and go from there ...
hope that helps