Heard back from Belbucus regarding the mono soundtrack:
While it might yield a useful reference, 16mm soundtracks have a fairly limited frequency response – around 150 to 5000 Hz with a dynamic range of about 40 dB. A 35mm Academy mono optical track is more like 45 to 8000 Hz with a dynamic range of around 48 dB.
From wikipedia, the linear track on a VHS tape has a frequency response of 100 to 10000Hz, so was probably a better source for the audio - certainly in terms of high-frequency content.