A nice addition to your toolbox is a set of fillers, for measuring piston to cylinder wall clearance.
They come in a variety of thicknesses but you only need a set consisted of 0.002, 0.0025 and 0.003 inch fillers. In metric system, above fillers measures about 0.05, 0.06 and 0.07 millimeters respectively.
You will have to measure the cylinder wall clearance at a 90 degree angle to the piston pin. Fit the fillers starting from the smallest size and install the piston until it slips into the cylinder smooth and tight and this will be your clearance. Consult your service manual for suggested clearances.
Use several pistons to get a feel of how the fillers react to different clearances and you will quickly realize that blindly fitting pistons, even when all parts are new is not always the way to go.
A very handy tool that can save you a seizure or other engine damage, especially when you are changing pistons in the pits.