[bryan chafy] has been hacking away to get older non VGA displays running on VGA hardware without using a scan converter. You can pick these old grayscales up for cheap or even free. The tricky part is modifying the BIOS to reprogram the VGA card to output a sync and scanrate that is NTSC compliant. He’s managed to do this with a WYSE Winterm thin-client. Another clever trick is the poor man’s triple head display which stores a different image in each portion of the RGB signal.