There is a program called vob blanker to do this. It's not for the weak of heart though
1. Rip PAL DVD to your hard disk with DVD Decrypter.
2. Used VobBlanker to open the decrypted files on the hard disk.
3. Changed Video Attributes from PAL to NTSC with VobBlanker.
4. Verify video attributes are set to 29FPS
5. Set output for VobBlanker to another directory.
6. Burn result to DVD from output directory with DVD Shrink.