This is 1976 without a doubt, although i don't have official documentation to prove it...On that tour, FM decided to test a few of the 'new' songs out including 'GYOW, YMLF, Gold Dust Woman,Don't Stop and Silver Springs'...yes, Silver Springs...they began that tour in June, 1976...I have a tape from Kansas City (6-18-76) from that year and they did all of the above songs (from the 'new album' which they announced was due in September) except for GYOW...I also have a tape from Milwaukee a few days later (6-21-76) and they only did 'Silver Springs and YMLF'...a month later in Cleveland (7-23-76) they only did YMLF...the "Rhiannon's" on these tapes are VERY identical to the Rosebud performance. Also, GYOW on Rosebud is more crude which led me to believe it was an early version of the song (no screaming guitar solo in the middle or end)...I don't have an exact date but i noticed that during some of the outside interview segments it looks like the outside of the Sausolito studio ( i could be wrong ) which would make sense since they were there in the first half of the year recording Rumours...I don't know what the dates are on the live performances that were recorded outside ('So Afraid', 'World Turning' from Rosebud and also the outtakes of 'Over My Head' and 'Rhiannon' from the same show that were shown on Disney's Going Home and VH1's Behind the Music respectively) but it was definately 1976. Imagine a Rosebud 'Silver Springs'???
I've been listening to the 1976 concerts the past few weeks and they're amazing...Rhiannon from Milwaukee has to be the best ending i've ever heard in my life! I get chills hearing it...she went on and on...it was a very extended ending and she had no trouble doing it...you can even hear the people in the audience going nuts during that...i can understand why, in Mick's book, he says Stevie 'shredded her vocal chords' that year singing the **** out of 'Rhiannon'.

Sorry to ramble! Hope this helps!