Rename your original pal pac to PacNamepalz.pac and the original ntsc-u pac to PacNameusz.pac. The to be converted file should be called PacName.pac (You are free to choose the PacName. Just be SURE not to end the file name with the letter z...)
The converter will convert all files with this name structure in the file the converter is in.
The difference between the two converters:
BatchPacConverter.sh keeps checking through differences between the original Pal and NTSC-U pacs (usually doing the whole proceedure in three loops) and converts the differences found to the modified NTSC-U pac file.
PacConverter.sh only loops once.
Tip; if a file doesn't convert using the BatchPacConverter.sh use PacConverter.sh.
Notes on the Windows version:
You'll need to install cygwin to run the script. Once you've done that, you can execute the the script from one of cygwin's subfolders using the command line (that's how I tested it). Sadly the windows version is emulated, and thus really slow (it takes almost five minutes to convert a single pac file. Still quicker than humans of course
)