Richard Gillis died on 31st July 2019:
https://www.hollywoodreporter.com/news/richard-gillis-dead-ballad-cable-hogue-songwriter-was-80-1231501

Apart from 'The Ballad of Cable Hogue' soundtrack and 'Blow the Gates to heaven', these are only other records I can find (all 45s):
'Tomorrow is the Song I Sing'/'Butterfly Mornings' (Promo for the movie. The first track is different from the two versions in The Ballade of Cable Hogue and the second is Gillis' vocal rather than Stevens/Robards on the soundtrack.)
'CB Santa Claus'
'Think It Over'/'Yesterday's Gone'