The only P&C that would be considered a big bore would be the 272 kit. Would require the different intake block and gaskets and likely some interference with the spark plug and top cover. Easy items to over come. OEM 266 cylinders are NLA, but if there are decent aftermarket ones out there I'd go that route as the 266 configuration is a good running saw.
But as already mentioned, most aftermarket cylinders fall short of OEM in heavy use situations. That fact is often distorted here because so many of us own so many saws that we don't put as much run time on a saw as someone who only owns one or two saws.