Modify SAR output

Is there a way to force the output ratio? I have an incorrectly flagged 720x576 .mp4 file that displays as 16x9 when it should be 4x3. VEAI displays the SAR as 1.46. I would like to convert to 1440x1080 with square pixels (and black bars at the side to give 1920x1080).

Any suggestions?