I made this modification a while back and the location of the handle, backing plate and latch mount cutout on the edge of the door ARE different. The handle moves forward and up slightly (about 3/4"), the mechanism on the edge of the door moves up also and its mounting holes are completely different.
The driver's door on my '52 half ton had the pull down handle when I bought it and the belt line did not line up at all. At first I thought it was just a door adjustment until I realized the handle was from an earlier truck. Passanger side was correct, driver's side was the wrong year (both door and handle).
Once I figured out the problem, I took measurements from the passanger side, transferred them to the driver's side and made a patch panel out of a VW bus roof section. I used the roof section because the curvature was a match for the door skin. Then I made a new plate for the door edge to receive the mechanism and welded everything in place. With a handle, latch mecanism, backing plate and striker from a salvage yard, the door works perfectly.
http://s1273.beta.photobucket.com/user/DMarcB/library/#/user/DMarcB/library/
