If you are prepared to just use the left or right channel as a mono recording then the obvious solution would be to run a recursive script that ran on all folders in the _data folder and deleted all odd or even numbered AU files.
I am not a scripting genius but you could search on Google or ask on the forum of the file manager program you used to do the sort and rename.
I would emphasise again that unless you used PowerShell or your tool really does sort each pair of AU files in the order they were created in, then some pairs of AU files will have right channel first. So don’t be surprised to find some discontinuities in your mono file where you actually have the other channel.
Gale