From a good source (old Dylan post from yourself, Rick Fielding), Bob Dylan was "Blind Boy Grunt" on a Folkways album.
OK, so we've got Scott Mackenzie for the Phillips question; Josh White for Ovation - think he tried the guitar at the Gaslight in D.C. (Mr. Kamin made one for Glen Campbell soon after); at least one of the two American groups was mentioned; so we're close but no Seeger yet.

Mark