!!!!!WARNING: DO NOT PUT AN X-RING OR O-RING CHAIN ON A CB500 OR CB550!!!!!
Many of the 750 guys don't realize that using an o-ring chain on a 500 or a 550 will eat through the engine case right behind the front sprocket. When you first install it everything seems fine, but there is some sideways flex that causes it to rub the case while riding. There's a big rubber seal back there that will be ruined, and the only way to replace it is to split the cases.
I caught mine in time, but others here have not been so lucky. Do a search to hear some horror stories.
I can't speak to the quality of JCWhitney chains, at all, but they do sell off-brands. I'd rather go with a known-good brand from someplace like MAW
http://www.accwhse.com.