Mama's Boys ???

I don't recall them at all ?

- but then, there are guilty reasons for black holes in my memory of the 70s....

The only Youtube's I can find are 80s videos of an average commercial pop metal band..

any better links to suggest ?

Thin Lizzy and Rory Gallagher are more obvious partial folkrockers who are easier to remember...

But my favourite mid 70s folk rockers were Jack The Lad [Lindisfarne spin off band]

Definitely had a more assertive, even aggressive, arguably 'proto punk' vibe about them...
even though they played predominantly 'acoustic' instruments...