Yep @hifiguy42, I figured so. I do have the Just Me And My Guitar album, on LP. The series of eight 2-LP chronologically-arranged Hank Williams compilations on Polydor are essential imo.
I would like to add to your list Lefty Frizzell (a favorite of Merle Haggard, and singer of "Long Black Veil", a great song The Band included on their debut album), Buck Owens, Johnny Horton (as a kid I started my subscription to the Columbia Record Club with his Greatest Hits album), Johnny Cash (my Mom had his Ring Of Fire LP, which I wore out on our Magnavox console), The Louvin Brothers (if you like The Everly Brothers you’ll like them), Webb Pierce, Ray Price, Carl Smith (Carlene’s Pa), Tom T. Hall, Charlie Rich, Faron Young, Ricky Skaggs, Jimmie Dale Gilmore, Vince Gill, Clint Black, Randy Travis, George Strait, Rodney Crowell (a great songwriter too), and Keith Whitley. Though categorized as Rock ’n’ Roll, The Everly Brothers have deep Hillbilly roots, and have made some purely Country Western albums.
And let’s not forget the gals: Wanda Jackson (a girlfriend of Elvis’, and a favorite with Rockabilly enthusiasts. I’ve seen her live!), Tammy Wynette (my personal favorite), Skeeter Davis (in the mid-80’s she did an album with NRBQ. She was at the time married to NRBQ bassist Joey Spampinato, who is Keith Richards’ favorite bass player.), Loretta Lynn, Kitty Wells (now THERE is a hillbilly!), Patsy Cline of course, Dolly Parton (when she isn’t pandering), Connie Smith (she’s married to Marty Stuart), Patty Loveless (I LOVE Patty!), Rhonda Vincent (also an excellent mandolin and fiddle player), Alison Krauss, Rosie Flores, and the Queen---Emmylou Harris!
The Grievous Angel album, being a various artists compilation, is a mixed bag. My feeling is that Gram was a much better songwriter than singer (he sings flat throughout his debut solo album. He’s much better on his second), so interpretations by other singers is fine with me.
By the way, I attended the Return To Sin City---a Tribute To Gram Parsons tribute show held at the Universal Amphitheater in 2004. It too was a mixed bag, the low point being the disgusting behaviour of Keith Richards, who was hanging all over poor Norah Jones, who looked horrified. He also sounded like sh*t. They sang "Love Hurts", a song thought by many to be a Parsons song. Nope, it was written by Boudleaux Bryant, and recorded and released in 1960 by The Everly Brothers. A FANTASTIC song! The Brothers version is considerably better than the cover by Gram and Emmylou.