NTSC video: 480 lines
PAL video: 576 lines
Cropped 2.35:1 NTSC non-anamorphic video: 272 lines
16:9 video optimum resolution for width of 704 pixels: 400 lines
2.35:1 video optimum resolution for width of 704 pixels: 300 lines
16:9 video anamorphic encode resolution: 480 lines
300/400 of 480: 360 (Target number of scanlines for Anamorphic 2.35:1)
272/480 of 576: 326 (Computed number of scanlines for PAL 2.35:1)
It may even be possible to fudge a bit, since, watching 704x480 instead of 640x480 doesn't look too noticeably distorted, neither would perhaps 704x326 instead of 704x360.
Moll.