I tried to do this and finally gave up. Here are the instructions I found in the tutorials for MPEG2 Works, using Mac the Ripper and then MPEG2 Works (
http://mac.sofotex.com/download-126993.html):
Ripping for conversion:
Use Mac the Ripper in TITLE/CHAPTER mode to extract the title you want (the one with MF in its name is usually the main feature). (READ THE DIRECTIONS for using Mac the Ripper - you have to let the program scan the DVD in order to set the extraction correctly according to the zone, and you may have to make some choices so that it extracts properly. I didn´t do this the first time, and regretted it.)
You will get one big VOB file. Now try to open the .VOB in Quick Time. If QT opens it, then your MPEG2 component is working. If not, you have to re-install a working MPEG2 component for QT, which you can purchase on the Apple site. That component is essential for MPEG2 Works and DVD converter apps to work with MPEG2 files.
Now - if you hear audio in QT, that means that your VOB has an .mp2 audio track and you can therefore convert it with the preset button of your choice in MPEG2 Works 4, in the "VOBs with AC3 audio" section.
Converting:
Use MPEG2 Works 4 Advanced to convert from PAL to NTSC (click on "VOB" in the menu, then choose VOB PAL <-> NTSC Conversion), and use MPEG2 Works 4 Advanced - Rec section - to create a burnable DVD VIDEO_TS folder.
I had problems once I got into MPEG2 Works. It´s been so long now, that I can´t remember what had me stumped, to be honest. If anyone figures this out, please post!
The MPEG2 Works program´s creator has a site with a forum, with a tutorial section. A search there will turn up many relevant threads on PAL/NTSC conversion:
http://www.mpeg2works.com/phpBB2/viewforum.php?f=6&sid=39487ba93196e9da7706f6c9097e775e