70 & 71.
I had heard 69 many, many times, but never knew it was a Zappa tune. Doesn't change my vote, though, as I really liked the ambiance and mood of 70.
71 had a few really great moments, and I enjoyed the hell out of it - proggy as it is. 72, though chock full of good playing, sounds like a demo track of different riffs or what would have been a really amazing solo section/bridge if it were placed in a longer song.