Try this one:
Mode "640x480i" 10.09 640 648 664 688 480 481 482 489 Interlace
This will only be a 60Hz refresh (30Hz Interlace), but that might be exactly what your projector needs if it is indeed intended for NTSC TV applications. The horizontal rate is 14.67kHz which is within the limit you specified.
Have you checked the HOWTO
The reason many modeline generators ask for the pixel rate is that older videocards often only had a few fixed pixel clocks that you could use. This made for an additional challenge in matching videocard and monitor specs. Any modern card will have a programable clock generator so this is not an issue (unless you try to exceed it's maximum).