This panel could be made somewhat easily, the big thing to remember about bending flanges around a radius is that the adjacent flange will need to be either stretched or shrunk, depending on whether the original panel should remain flat or form a radius. Using the following to explain further:
http://s5.photobucket.com/albums/y1...iew¤t=RadiusedFlangedPanel.png Where a 12" wide panel has a 1" flange bent, in order to put a radius across the panel you'll need to shrink the flange. Notice in the drawing, at the bend, the dimension remains at 12", halfway up the flange needs to lose about 1" in length, and at the edge of the flange, you need to lose almost 2" in length. So shrinking is used on the flange, and is done in a stepped fashion to provide more shrinking toward the outside of the flange:
http://s5.photobucket.com/albums/y1...?action=view¤t=ShrinkDemo3.png In your case, the part up top that tucks under the roof leading edge is about the widest of all the folds, so I would start with that shape as the "original panel", and the remaining flanges we will call fold 1, 2, and 3. As opposed to the sample shown above, in this case we would want the original panel to remain somewhat flat. Looking at the proposed layout of the repair piece linked below, I would start with a cardboard/posterboard template of the upper section (outlined in black) and sufficient material below (outlined in red) to perform the remaining folds.
http://s5.photobucket.com/albums/y1...on=view¤t=Windshieldrepair.jpg However, as the flange (fold 1) is folded outward, (outlined in red) with the outer edge of a shorter length, it will tend to pull the original panel into a radius as you bend, similar to our sample panel in the first link. So in this case, we would need to stretch the folded area (primarily in the area in yellow) to maintain the original panel as flat. I'm sure it's not exactly flat, but the correct contour/radius could be achieved by the amount of stretch introduced into the fold.
Now once you have the fold bent at a 90 (if that is the proper degree) and stretched so the original panel matches that of the truck, now you need to perform fold two. In this case, as you are trying to bend the fold downward and in trying to force that into a smaller radius, you will need to shrink the outer flange as you perfom this fold. Otherwise, the excess length will attempt to push the original outward, for less of an arc. I would suggest performing this in increments, fold some, shrink some, repeat. If the width of the remaining flange seems excessive for a Lancaster style shrinker, then I would use the contraction with heat method, heating in a VEE pattern and cooling to shrink. The wide part of the vee would be located on the outer edge of the flange, as that would need more shrinking. Alternatively, tuck shrinking would work as well.
Once that matches the truck, then move on to fold 3, which will be very similar to fold one, you will need to stretch again, especially in the radius at the top corner of the windshield. With some patience and precision, this is very much a panel one could duplicate. The other option in making a replacement panel would be to use a hammer form, but that would take about as much time in itself as making it by the above mentioned method. If someone were to make multiple quantities of this panel, then the hammer form would be more advantageous.
