Hello
Do the framrate conversion when you do the AC-3 to WAV step. Then just feed your wave into TMPGEnc to get a MP2 audio file (assuming you use TMPGEnc for doing video).
Once you have the WAV file at the correct fps you can actually use ANY program that will convert it to MP2 ... not just BeSweet or TMPGEnc.
I've had trouble using BeSweet to go straight from AC-3 to MP2 while doing the framrate conversion. Hence I just convert the AC-3 to a WAV (doing the fps change in that step) then feed the WAV into TMPGEnc Plus 2.5 while I'm doing the video encoding.
- John "FulciLives" Coleman
P.S.
I have a funning feeling (or guess if you will) that if you change the fps in the AC-3 to WAV step that BeSweet will then be able to take that "corrected" WAV and turn it into a MP2. You might also want to try going from AC-3 to AC-3 (doing the fps change) and THEN go from the "corrected" AC-3 to MP2 and see if that works.