When I put 8 on my G73SW-BST6, I just used the Win7 64 bit drivers. They work, but if you go looking around a bit, you can find more modern versions of them that are expressly for WIndows 8 and 8.1. Lists like
this are pretty cool, as they'll usually give you a site and version number, and you can search from then onwards to whats needed.
I've also used
this post and
this link's listing to find my modern copies. One of these here links has pointers to more modern ASUS progs and drivers, like the Fresco USB 3.0, the Keyboard Filter, the ACPI stuff...just go looking around.
I'm planning on doing a full reinstall within a few weeks, so if I get a solid methodology, I will post back a full list of drivers I used.