You cannot "assume" you can use standard rings. If you want to do it right, you need to measure the cylinder bore to see if you can use them or if you should bore the cylinder. There is a tolerance with every engine set by the manufacturer as to what is "out of tolerance". You can usually find these specs in a Haynes manual or the like. You also need to measure your cylinder for taper (top to bottom) as well as for out of round. Each of these will have a tolerance as well. You also need to check the piston itself for wear. You may have rust scoring on the cylinders, which would need to be taken care of (usually by boring the cylinders). If you have to bore the cylinders, you'll need new pistons as well. Pistons have a measurement check on them. You'd need to use a micrometer, usually at the top of the skirt. The portion of the skirt which is on the thrust side of the piston usually gets the most wear. Again, these specifications can be found either online or in a rebuild manual like Haynes puts out.
All that said, you may be able to get by with a re-ring and honing the cylinder walls. This would be the bare minimum you'd need to do to replace the rings. In order to do this, you have to tear the engine apart. It only makes sense to put new bearings in while you're at it.
