Ditto on the 3 9/16" standard bore. That's 3.5625" in decimal measurement. A .040" oversize cylinder should measure 3.6025" if it's not worn oversize. The majority of the wear in a cylinder happens in the first 1 1/2" of piston travel at the top of the bore, so it doesn't wear uniformly from top to bottom. If there's more than .005" of taper wear, a ring job usually won't last long due to the piston rings constantly changing size trying to maintain contact with the cylinder walls.
Here's a quick way to check cylinder taper if you don't have an inside micrometer or a dial bore gauge. Take a compression ring off one of the pistons and place it in the cylinder at the top of the ring travel. Square it up in the bore by turning the piston upside down and using it to align the ring in the cylinder. Make sure you don't measure at the very top of the cylinder, because the rings don't travel that far up the cylinder. Stack up blades of a feeler gauge until you can measure the ring gap accurately. Record the measurement. Now use the piston to push the ring down to the bottom of the ring travel, or at least close. This depth isn't critical, because there will be very little wear if any at the bottom. Measure the gap again. Subtract the bottom gap from the top, and divide the remainder by 3.14. That's the cylinder taper.
Example:
Top ring gap is .035" Bottom gap is .020" Difference = .015" .015 divided by 3.14 = .004" taper. You can glaze-break and re-ring this cylinder. The taper isn't enough to fatigue the rings and cause a short-life rebuild.
Jerry
Edit: The piston diameter at a 90 degree angle to the wrist pin and the same height as the wrist pin from the top of the piston should be about .002" smaller than the bore size. The piston is egg-shaped, with the largest diameter at the center of the skirt, so be sure and measure it at its largest diameter when it's cold. It gets round as it heats up due to its internal construction. To cure a sloppy-fitting piston during a rebuild, we used to run a knurl on the face of the skirt. Surprisingly, it worked pretty well. Chevy cast iron pistons wouldn't take a knurl, so there was a spring steel expander available that got installed inside the skirt with a special pair of spanner pliers to cure piston slap on those engines.
Jerry
