My impression was that the sign had first noted Lefty Frizzell -- and Lefty only.
As Sheb made his mark, his name was added.
Then, finally, along came young Roger -- Sheb's cousin, by the way -- to require another amendment.
But as for "body of work", I would agree with you. Lefty first, by a hair, just ahead of Roger.
But "King of the Road" ranks ahead of "Long Black Veil"...
Even though I've seen the sign numerous times, I always discounted it because I truly thought Lefty was really "for real" from Saginaw, Michigan.
Possibly the son of a Saginaw fisherman, but that part didn't matter.
After my dad got a speeding ticket in the speed trap of Saginaw, Texas (where the big grain elevators were by the RR tracks), while on one of our numerous road trips, that was our song when anywhere near Foat Wuth.
Now, thousands of people live there and the speedway is there ... but back then, it was an empty highway coming in from Oklahoma and those were the biggest "buildings" on the horizon - those grain elevators.
Then we'd smell the stockyards and know we were almost to FW.