Anamorphic is generally not extra width, but actually less height. Unless you’ve got a very expensive camera. It actually uses less of your CCD, the center 16:9 part, and then stretches it vertically to fit the 4:3 ratio.
But either way, just make sure you tag it as 16:9 footage and drop it in your non 16:9 sequence. Scale it up until it crops out the “extra width.”