its a straight fit with some minor modifications (well it is when changing from 4dr lights to 2dr lights)
from 4dr to 2dr you will need:
2dr bootlid
rear bar
both taillights
to make the taillights fit, you gotta cut away abit of the metal where it slots in to make it sit neatly, at the bottom of the boot, you will need to weld a 5mm metal strip on to make the gap as small as possible like as if it was an original 2dr rear. you can get away without welding the metal strip on but the gap from the rear boot > rear bar (above where it says skyline) will be like 2cm or a bit more.
i assume it would be the same when going from 2dr lights to 4dr except for the welding of the metal strip and cutting away some metal to fit the taillights.
if anyone wants to do it, im willing to be up for a swap (ive got a 4dr) preferbly a silver skyline
i like the 2dr lights better, much more agressive and sexy looking