I found this video for Best I Can on YouTube. The footage is from Don Kirshner's Rock Concert TV show. It's really grainy and the audio isn't synched up too well but it's still cool to watch. 2 other songs from this episode were included on the R30 bonus disc; In the Mood and Finding My Way from Rush's first album. Thanks to YouTube member eljulian for making this available.
UPDATE - 3/1@9:24AM: I also just found the Don Kirshner's Rock Concert video for In the Mood.
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