It depends if you are using slow down or just pulldown flags.

I'll assume slow down since that covers most movies. (If you aren't slowing it, just skip step 2).

I really need to make up a full PAL2NTSC guide, but here's the subtitles part (I like to avoid converting to text format on the way since I'm a purist):

1) With Vobsub Configure: Click Open and select the original ifo/vob on the PAL DVD. This will rip your subtitles in idx/sub format.

2) VobSub Cutter: Open your ripped idx/sub file, uncheck 'Modify Time Stamp Count From Start'. Check 'Modify FPS'. Original: 25, New: 23.976 (of course). Click Save As and save your newly retimed idx/sub files.

3) SubToSup: Open new idx file and they will be saved automatically in SUP format for use in MuxMan.

4) Although some DVD players are ok with this final DVD, you'll really want to load your final files into DVDSubEdit and adjust the vertical position of the subtitles to correct for the change from 576 to 480 lines of resolution (or your subs may fall below the screen).

I've tried tweaking the .idx 'Original Frame Size' and 'Scaling' to do this, but it doesn't seem to change anything. I believe most of the information stored there is for PC playback but is thrown out when coverted to a SUP file.

[Off topic] I use MuxMan instead of DVD Lab because it allows me to build a bare bones movie with graphical subtitles and corrected celltimes (which often includes more than just chapter stops).

I then use NuMenu4U to do a full conversion of the PAL menu system to NTSC, followed by VobBlanker to replace the PAL movie with the one created in MuxMan. [/Off Topic]

If you prefer DVD Lab _IN THEORY_ you can use VSConv to convert the idx/subs to Maestro format (which is a SON file and a BMP file for every title). It is one of the few graphical formats compatible with DVD Lab.

I put this method together after much trial and error (and swearing). I hope it helps you.