Professor H has traveled in his wayback machine all the way to 1965 to bring us this glimpse of the Juggernaut's original design by Jack Kirby and Alex Toth.
The image was found in blue line under the original art. Alex Toth used blue line pencils while Kirby usually did not, so it's unclear who actually came up with the final design for Juggernaut. The article accompanying the image also mentions that the notes on the border of the artwork imply that Kirby intended to have Juggernaut be the one to cripple Professor X. Kirby didn't yet realize that Stan had revealed that Lucifer crippled Professor X just three issues earlier, since that apparently wasn't part of Kirby's original plot for that issue. Juggernaut's real name, Cain Marko, was most likely an allusion to the biblical Cain who invented murder by killing his own brother.
The complete article appears at the Kirby Museum:
And as always, Professor H's marvelous wayback machine can be accessed via the link that follows: