Just sell it and buy a GTR, its going to cost you more to convert it than it is just to buy a GTR.
AWD compatible engine (like from a GTR or a awd stagea... as the sump is different because of the front diff), gtr transfer case, gtr front diff, gtr rear diff (front and rear diff have to be the same ratio, I dunno if the gts-t has the same final drive as a gtr), attessa unit, g sensor (2k for a genuine working one from nissan as I saw in a R32 buildup thread, easily damaged so i would be worried about a 2nd hander).. just to name the obvious