You might want to try the steps that people have done to get it to work on DW20's 1.6.4 pack. There was a thread or three floating around that had steps to do it; I forget if it was in FTB General or Mod Discussion.
Either way, unless you absolutely require Optifine to be able to play, I'm still of the opinion that Optifine does more harm than good and should be avoided unless absolutely necessary.