You should be able to set the pixel aspect ratio to 1.33 in your composition and on your footage. It should display correctly then. It should be under "interpret footage" setting for the footage and Comp settings for the comp. It may vary depending on what version of AfterFX you have.
A workaround is to put the 960x720 in a 1280x720 square pixel project and stretch the video horizontally to 1280x720.