Is there a way to get headac3he to do a timestretch to correspond with a framerate change? I know Besweet can do it, but I can't figure out how to do that in headac3he.

You can't.

You can use the free soundstretch program to adjust your wave file, or you can do an assumefps in avisynth. Soundstretch may introduce a slight delay where your audio and video may be slightly out of synch by the end of the movie.

If you write a simple avisynth script like:

AviFileSource("videoname.avi", true)
ResampleAudio(48000)
AssumeFPS(23.976, true)

You could use Avs2Wav to extract the audio from the script, the resulting wav is then your preferred fps rate (here it is ntsc film at 23.976 but it could be 25.000 Pal).

Hope it helps

__________________
Dave