I've been told by cat that the blocks are the same. What makes the NXS a 15.2L is the crankshaft. But both have the same bore. Cat told me as long as I'm using the 6NZ crankshaft, rods, pistons, liners and everything else from the 6NZ engine that I wouldn't have any problems. And being that I've already purchased the NXS block I'll be sure to report back and let you know what happens.I don't know if I understood your question correctly, but the answer is if is just to replace the block it self, no, two totally different blocks 6NZ is 14.6 litter, NXS is 15.2 and that is via a crank shaft, you could replace the long block with a long block NXS but not just the block to fill with all the 6NZ pistons and con rods and rest of the stuff.