My 2.0 sync varies probably more than you'd like, and the PAL ROTJ sync slowed down will (I think) vary from NTSC sources on the dialogue due to the different ADR.

Your best bet on a reference AFAIK is my 5.1 hairy_hen remix, most of the sync is very reliable (because I didn't do it!), except for the <1 second of audio that I put in, which may vary by a few ms either way. But that <1 second is probably what you're looking for...

If you want it, PM me and I can deliver it in AC3 format. The trick is you'd have to downmix it to stereo, and that may cause its own complications.

Honestly you'd probably get the best results by using an NTSC sync (which you presumably already have) and adding/deleting the frames yourself. Or you could release it synced to NTSC (w/ perfect sync) and let others make PAL-framecount-synced versions (with looser quality control).