Topic: saving config files across build/installs - and system type?

When I put 7.06 on a Buffalo WHR-HP-G54,  I had found a way to preserve my configuration file changes across the plethora of builds.

I started from scratch on the latest trunk, for th Buffalo, and WRT54G (currently on dd-wrt) - and can't find any reference to where in the build tree I can stash the /etc/config/* files so they wind up in the firmware.

I want to get OpenWRT across the board, to ease management, and because after putting trunk on the Buffalo, pings from a device on one AP to a device on another AP (both in AP+WDS mode), returns duplicate answers.

Relatedly, since I want to manage several APs from the same build - can anyone point to me how webif (very nice, by the way - I'm a CLI guy, but tried webif just to see how it was comming) determined that it was running on a Buffalo WHR-HP-G54?   I'm looking for a way to identify which AP the code is running in - so the scripts can vary things like firewall rules, routing, etc.