So I got spooked by the original DV-avi file size and compressed them to mpegs. I went back to the original dv-avis (which were occasionally too long because I left the VCR/ADVC running), trimmed them up, and used them (in all their 28Gig glory) and the syncing was better than ever.
I noticed vegas could much more accurately sync the audio-video with those files than the original old mpgs I was given before I recaptured the tapes. Also, the ADVC gave me a way larger audio ceiling – there was clipping all over the place on the old mpegs I was given (captured straight from a VCR with USB), audio was in general much cleaner as well.