I'm trying to convert the audio files from an old protools version where the files were headerless and lacked any other indicator of format.
In this case, the answer is sample rate: 44100, 24 bits per sample, signed integer, Big Endian.
The converter I'm using, "sox", is available on Mac via homebrew, and the commandline I used is:
sox -r 44100 -e signed -b 24 -B -t raw "Guitar --01 L" Guitar-01-L.wav
Some of these parameters might be different, depending on what choices you made for the project, but I'm pretty sure these were the default on Mac OS 9 on a PowerPC mac at the time.