4.8125", or 4+13/16", is getting pretty close to an absolute max for general boring on a G jug. I personally do not go that big. I have seen a few cylinders start to pin hole fail at that diameter. MM offered 4+13/16" pistons, for a short time. They stepped back to 4.751" true finished bore diameter and never looked back. At that diameter, problems all went away.
There are a lot of sixty, ninety, and one eighth inch overbore pistons out there that will fill the bill, and replace the original pistons. Many are using Dodge pistons and using a thick walled bushing to go from 1.0625" to the 1.25" pin diameter needed to use G rods.
To select a piston for your needs; you need a piston with a 2.843" compression height to equal the old original MM pistons.
Charlie at Moline Parts