How can I convert from the default m4v extension to mp4 extension in Compressor?

I use Compressor. A client wants me to convert from the default m4v extension to an mp2 or mp4 extension. I've gone through Compressor settings for MPEG2 (the only MPEG offerings I can find) but they don't allow customization. For example, the aspect ratio is set at 4:3 and the bit rate is at 15Mps and are grey. Neither setting is acceptable for the client. Any suggestions? Thank you.