Yes. Edit your show then send your master to be converted on an Alchemist or other high quality hardware converter.
You can do it on the cheap, using Avid mix and match...copy your final sequence, do a video mixdown of it and replace the video..open the new sequence in an NTSC project. There should be a green dot on it, indicating a Motion Adapter has been applied. This is not as high a quality conversion as a real hardware conversion, but may be acceptable in some situations.
If all your assets are PAL and your delivery is NTSC, I would edit in PAL and wait till the end. If only one of your assets is PAL amongst TSC assets and delivery, then I would open it in a PAL project, then open that bin in an NTSC project so the mix & match will kick in and 50 fields will be adjusted to 59.94 fields while maintaining audio sync.