FWIW, there's a PBS special (called "The Last Of The Breed" or something like that) featuring Willie Nelson, Ray Price, and Merle Haggard -- it seems to be a pretty recent concert and has been airing on various PBS stations this summer and fall.   Merle sings the song in this concert and, if memory serves me, he does give Lefty credit as the songwriter (and as one of his main influences).

As for the chords, they aren't really hard. It's just that in the key of G, that transition from Am to D7 on the phrase "horse-shoes" (or "love goes") is a bit unusual (not to mention effective).