Okay, so in my Leone film thread, it was noted that the mono mix for Duck, You Sucker/Once Upon a Time...The Revolution was mastered in lossless 2 channel DTS-HD MA, but that one channel had a short delay, and the ending was kept in Italian.
So, working with the original DTSHD-MA file, I used the left channel, as it was the more precise of the two, and filled in the 2 instances of Italian at the ending from the 5.1 AC3 HDTV file (downmixed, of course).
However, while the first line (Johnnieeee!!!) felt seamless, "What about me"'s background sound effect sounded slightly different than the Italian mix, which creates a slight dissonance, but only for about 2 seconds, as the rest is the original lossless audio.
However, unless someone has a better source for that last line, this will certainly do.
V1.5 update: Lil Brutto generously provided me with the lossless LD audio containing the missing lines, and I have updated the file accordingly. The LD audio has the original sound effects, but has a slight hiss, so the change in source is still noticeable, but a lot less jarring than V1.
I exported in 1 channel PCM WAV, and it synches perfectly with the Italian BD.