How are you 'checking' the sync? I'm guessing you're down-mixing the AC3 to a 2-channel wav then using wavsource and audiodub in AviSynth.
BTW: 64514 frames - 44 min 51 sec is correct for 23.976fps video.
83100 frames - 57 mins 47 sec is 1s out (should be 57m46s).
Is LD ac3 48kHz or 44.1kHz?
It's 48kHz, 384kbps.