Hello all.
Plastic Jesus is an old folk song, and like all old folk songs, there are as many versions of it as there are people who sing it. Seems that everyone who sings it (including Paul Newman) sings a different version. Personally, I think Paul Newman's rendition is about the best I've heard. I have included links to lyrics for several versions of the song at the bottom of this post.
Ernie Marrs is given credit for writing the song when it was published in Sing Out! Magazine in 1964, but there were earlier versions at least as far back as the 1940's. You can go read all about it here.

As for the version Paul Newman sang in Cool Hand Luke, here are the lyrics and guitar chords. Sorry, but I don't play the banjo, so I couldn't tell you the tabs for that:

Starts out slow, then speeds up at the second (Get yourself a sweet Madonna...)

C
I don't care if it rains or freezes
F
Long as I got my plastic Jesus
C
Sitting on the dashboard of my car
D

C
Comes in colors, pink and pleasant
F
Glows in the dark because it's iridescent
C
Take it with you when you travel far
D

C
Get yourself a sweet Madonna
F
Dressed in rhinestone, sitting on a
C
Pedestal of abalone shells
D

C
Going ninety, I ain't scary
F
Because I got the Virgin Mary
C
Assuring me that I won't go to Hell
D

C
Get yourself a sweet Madonna
F
Dressed in rhinestone, sitting on a
C
Pedestal of abalone shells
D

C
Going ninety, I ain't scary
F
Because I got the Virgin Mary
C
Assuring me that I won't go to Hell



C       F       D
************
X       X       X
3       0       X
2       3       0
0       2       2


Other versions/parodies of "Plastic Jesus":
http://www.whitetreeaz.com/plastic_jesus/
http://ma141.tripod.com/data/plastic0.htm

Hope this answered some questions/requests.
Stephen Farris