Piston Selective Fitting When New Cylinder Block is Used:

WARNING: This page is about a different car, the 2004 Nissan Titan. However, it is still accessible from the selected car via links, so may be relevant.

Check the cylinder bore grade on the bottom face of cylinder block, and select the piston of the same grade.

Fig 1: Checking The Cylinder Bore Grade
Courtesy of NISSAN MOTOR CO., U.S.A.

Fig 2: Checking The Piston Grade
Courtesy of NISSAN MOTOR CO., U.S.A.