I have a Web 58a in one street job my wife rides. It's a mild improvement, probably like a 650 cam?? Not sure about the 58b, it shows a little more duration and the same lift.
I think with your choice of pistons & compression the Megacycle 12620 will make you smile. That's the one I race with and in the smaller displacement and 29mm carbs it has a weak spot around 6K at WOT. In a larger engine with similar carbs it should work great. Don't even consider the MegaX6.