[miniman82]

If you have a DVD player that has component output, hook the Y line into the set right after the detector. You won't believe the difference!

Barring that (you don't get sound unless you hack the audio section as well), you'll need to filter out the 3.58 info to get rid of the dots. It's really bad on a Philco-Ford set I just got (which is color but still suffers), the dot crawl is atrocious. I don't think it properly filters out all the info for the chroma section, there's obviously still 3.58 in the luma. Some kind of tuned trap is what you'd need, good luck with that.

I've been toying with the idea of feeding the Y and audio lines right into my Magnavox modulator, and feeding the TV with that on channel 3. Maybe you can do something similar?