I have read in the Rolling Stones that members of Zeppelin and Black Sabbath were good friends. Plus there was times when Bonzo would sit in on drums with Sabbath during rehearsals. Has any recordings ever been found of this?

The led Zeppelin 3 companion disk is worth it's weight in gold. Coda companion disk rocks. All the others are lame and not worth a second listen. Page enough already.

Me with my Zeppelin Tee in Guangzhou China