Pathfinder is actually fairly steampunk-friendly, which is why I like it so much. My group just started a steampunk game set two hundred years after a major war between technology and magic kind of messed up the inner sea region.
The Ultimate Equipment guide has a whole page or two on firearms from the basic musket up to a six-shot revolver, as well as a small number of magic items for firearms. One of the old Eberon campaign settings has rules for airships and other vehicles that use bound elementals as a power source.
There's also a 3rd party class called the artificer that blends magic with guns and fits well in a steampunk setting. We have one in our group.
If you haven't found it though,
this website is Paizo's official Pathfinder site, and has almost every bit of information their books have, plus a ton of 3rd party stuff that you can look up.