"So we combined the two using Final Cut Pro. It was a BITCH because there were numerous cases of a frame or two missing from the beginning of shots on the DVD. That meant lots of resyncing. Oh well. Them's the breaks."
Was this difficult? In Vegas, I can load both soundtracks, and visually line them up using the waveforms (and then listen to check for sync.) When I was comparing the Def. Col. and Faces soundtracks, I played them simultaneously through my headphones, one in the left channel and one in the right.