While digging around for information/pictures of the Music Box in Omaha, site of the GD's 2/4-5/69 performances, I found this little bit of trivia from http://www.nebrocks.org/bands.asp?band=48, a page about Mark Dalton, a bass player from Nebraska.
By 1968 - Dalton moved back to his blues roots, forming The Liberation Blues Band (1968-69). They played hard blues and were known for their lengthy jams. They performed at early FAC Parties at Der Loaf & Stein in Lincoln & were the first electric band hired by The University of Nebraska to play an outside show on the steps of The Sheldon Art Gallery. They frequently played in Omaha's Old Market, and in 1969 opened up for The Grateful Dead at The Music Box. There you have it. The question that had been driving us all crazy - just what band opened up for the Dead on 2/4-5/69? - has finally been answered. ;^)