Well, my xf86-video-ati package has these two files:
So you could just move them there and overwrite the old ones (and simply reinstall from the package manager to revert to the old one).
I think you can use this to see where your X.org server looks for modules:
X.org also has this in the Xorg manpage:
So you could probably use
Set the module search path to searchpath. searchpath is a comma separated list of directories to search for Xorg server modules. This option is only available when the server is run as root (i.e, with real-uid 0).
sudo X -modulepath /opt/xorg/<wherever your modules are there>