Well, that's a tricky one. Dolby 2.0 is what you're looking for, same thing. NTSC DVD authoring software needs MPEG-2 for video, and either AIFF or AC3 for sound. If I were you, I'd try to find a professional house that can convert an already authored DVD from PAL to NTSC. And I'm not sure that's very common.
Are you going to re-author the DVD from scratch? That's the best way to do it. What system are you working on, FCP, Avid? Windows, Mac?
