Start with the preset in Apple>Format>Quicktime>Uncompressed 10-Bit (or 8-Bit)
Click on Geometry Tab
Source Inset Cropping
Crop to 4:3 1.33:1
Dimensions (encoded pixels)
Frame size: 720×480
Default for size
Output Image Insert (Padding)
Padding 4×3 1.33:1
Click Save As and you should be good to go. Of course it is cropping the right and left of the image.