As Aroyo says, go the C-sync route first. This should work perfectly for 240p content, and might also work perfectly for 480i/576i content.
Sometimes those old Sony's get a bit flickery with interlaced modes depending on how sync is combined, and at what levels. I have a few 2730's, and those are using a resistor in each sync line, them combining, to get the best results. IF you want to try this, start with a 500R resistor and a 1k pot in each sync line, then merge into another 1k pot, then feed into the set's sync pin. Leave the last pot at zero and dial the other two around and watch what happens to the flicker. If this works, add 1k resistors in front of the pots, and go again. I'm suing between 2-3k in each horizontal sync line, and then about 4-6K in each vertical, then about 1K on the combined line.
This makes the image much more stable for me. It's still interlaced, but the flicker is minimised. My PVM-2730's are PAL models, so they will decode NTSC fine, but the circuitry works and looks best at 50Hz. Yours may differ. I can also use the Extron 190F i have and get just as nice a picture, but i only have one of those. Using Viletim's N64RGB mod, however, is instant headache city. The picture jumps around so much it's not watchable. I know Tim is a genius, so the sync must be perfectly within standard, it's just not giving perfect results in this case.