No, for true widescreen, you leave it as 720x480 (assuming you're talking NTSC) and +make it anamorphic+. However, this assumes you shot it that way.
If you didn't (i.e. you shot it as 720x480 non-anamorphic 4:3) this won't work. You'll need to letterbox it (giving black bars) or enlarge it (losing resolution), neither of which is "true" widescreen.