DVCPRO HD is usually 960X720 I believe.
In Compressor, choose a format preset that matches your sequence.
Turn Frame controls on. (You need to save as or duplicate a preset)
Set the frame controls to best. Create a DVCPRO HD file.
You have a challenge though b/c you have a 4X3 file. You could just blow it up straight and put black bars across the top and bottom, emulating widescreen too as an option.
Chris Tompkins
Video Atlanta LLC