It can be done relatively cheaply like mine - stock pistons rods etc - just new rings bearings and rod bolts. You can get adapters for more like $400 these days.
But if you're going to all the trouble anyway and its for your GTR you may as well do the forged pistons, possibly rods, fully balanced new harmonic balancer etc in case you decide you want to rev it to 8000 and make 500kw down the track.