Mark, the door hinge patterns definitely changed during the 1951 model year. The '51 Henry J section of the parts manual lists them as different parts but makes no mention of when the change occurred. They are:
"Hinge complete (with Center Hole 1 1/2" from butt end) 212982"
And because only one hole is moved, there are seprate ones for the left a right in the other style
"Hinge Complete, right (with Center hole 2 1/8" from butt end) 213047"
"Hinge Complete, left (with Center hole 2 1/8" from butt end) 212983"