Sure, O1 could be good but in a longer blade you'd have to be careful, as the high carbon content (~1%) might lend itself to be brittle after a conventional heat treat.
Before we decide fully on a blade, what kind of sword you planning on making (Japanese-style, Filipino, European)? What kind of use do you want it to tackle? There will be a variety of options available for different applications.
That said, you cannot go wrong with 5160, though it may not be 100% optimal in all conditions. Let us know what you intend to do with it and we can help you a bit more.
Shinryû.