[dsraven]

these old trucks probably didn't fit that well from factory so the "fitters" likely did what most would do when the door doesn't fit, put a knee below the window area, grab the top of the window channel and give it a pull. maybe thats what has happened to your door? possibly reverse the scenario to bend it back the way it came? wood block in the door opening and close door against the block to see if the door will "move" back like it was without oil canning?
again, a pic of what youre dealing with may help.