I believe that you can use the floor of a B13 without modifications until you get to the rear. The driveshaft doesn't need a lot of clearence since it only spins and doesn't travel up and down like a solid axle car.The rear suspension on the GTiR is assembled to a seperate bolt in subframe that you would need to fabricate strong mounts for.The Sentra and Pulsar/Sunny GTiR both share the same wheelbase and trackwidth so the parts can "easily" be made to fit if you have the requisite fabrication skills and an understanding of the basic systems.One final thing:you must use the exact same tires and gear ratios on all 4 wheels or you will grenade the transfer case.