The Folkswingers

http://www.allmusic.com/artist/p33538/biography

... the Folkswingers did an album on the World Pacific label in 1963, 12 String Guitar!, on which a pre-stardom Glen Campbell's 12-string guitar playing was backed by three members of the Dillards (Rodney Dillard on guitar, Doug Dillard on banjo, and Dean Webb on bass).

The Folkswingers made at least 2 more albums: 12 String Guitar - vol 2, and Raga Rock.

Did they play folk? Dunno. Someone out there in the interwebs reckons The Folkswingers had absolutely nothing at all to do with folk music or with swing either ..... What do you think? I can't find anything from the 12 String albums online. The 1966 Raga Rock is easily accessed.

As you say, pinz: team The Dillards with the quality picker that is/was Glen Campbell and the output has a fair claim to be called 'folk' (the material choice doesn't detract, either).

You probably knew - but Capitol chose to team Glen with The Green River Boys for his first ever LP release (under the GRB's moniker), the also very rare 1962 Big Bluegrass Special. I found a rip of the LP online recently - and it really is a fine album.