Versions with "!" are definitely (among) the versions that inspired Nick.
Versions with "1" are first recordings of the song.
From Her To Eternity:
Avalanche ! Leonard Cohen
In the Ghetto ! Elvis Presley
The Firstborn Is Dead:
Wanted Man 1 ! Johnny Cash (written by Bob Dylan)
Kicking Against The Pricks:
Jesus Met The Woman At The Well * Mahalia Jackson
Jesus Met The Woman At The Well * The Five Blind Boys of Alabama
Jesus Met The Woman At The Well * Fam. Blue Jay Sing. Birm. Alab.
Weeping Annaleah 1 Mickey Newbury
Weeping Annaleah ! Tom Jones
Something's Gotten Hold Of My Heart 1 ! Gene Pitney
Long Black Veil * Johnny Cash
Long Black Veil * Lefty Frizzell
Long Black Veil * Les Paul And Mary Ford
Long Black Veil * The Band
Running Scared 1! Roy Orbison
Black Betty 1! Leadbelly
Muddy Water ! Johnny Cash
All Tomorrow's Parties 1! The Velvet Underground
I'm Gonna Kill That Woman 1! John Lee Hooker
The Folksinger 1! Johnny Cash
The Carnival Is Over 1! The Seekers
The Carnival Is Over (Stenka Rasir) * Schwarzmeer Kosaken Chor
By The Time I Get To Phoenix * Glenn Campbell
By The Time I Get To Phoenix * Johnny Rivers
By The Time I Get To Phoenix * Tom Jones
Hey Joe * Jimi Hendrix
Hey Joe ! Tim Rose
Hey Joe 1 The Leaves
The Hammer Song [Kicking] 1! Alex Harvey Band
Your Funeral... My Trial:
Long Time Man * Tim Rose
Tender Prey:
I'm Gonna Run To The City Of Refuge * Inspired by: Blind Willy Johnson
Henry's Dream:
When I First Came To Town * Inspired by Herdman, Hills & Mangsen
When I First Came To Town * "Katy Cruel" (Traditional)
Live Seeds:
Plain Gold Ring * Nina Simone
Murder Ballads:
Death Is Not The End * Bob Dylan
Stagger Lee * Stagolee (traditional)
Kitchee-Kitchee Ki-Mi-O * Froggy Went A-Courting, Bob Dylan
Henry Lee * "Young Hunting" (Traditional)
The Willow Garden * "Down in a Willow Garden" (Traditional)
Knoxville Girl * "Oxford Tragedy" (Traditional)
Other releases:
Fever * Little Willy John
I Put A Spell On You * Screaming J. Hawkins
500 Miles * The Seekers
Rye Whiskey * Tex Ritter
I Just Dropped In (To See ...)(Die Haut) * Mickey Newbury
Helpless * Neil Young
Cindy, Cindy * Elvis Presley
Tower of Song * Leonard Cohen
Rainy Night In Soho * The Pogues
What A Wonderful World * Louis Armstrong