The actual image resolution before scaling was 704 x 324 - because I trimmed 16 (mostly black) pixels from the left hand side. This image was upsampled vertically to 324 x (16/9 ÷ 4/3) = 432. To convert to NTSC, you need to downsample vertically to 432 / (576 ÷ 480) = 360.
Unless you're talking about the "analogue" horizontal resolution of laserdiscs which isn't really relevant when talking about pixels. Even then, the vertical resolution or number of lines is fixed at 576 (324 for the actual image).
Scaling down then back up is just an extreme form of noise reduction!