When I've done these in the past, it's the door that matters not the fender. So, I suggest cut out all of the old, position the new w/ tacks, and then install the door w/ hinges to confirm alignment. The door to quarter panel gap and the rocker to bottom of door define the proper position. Watch out and do not mount the post too far towards the rear - if you consume the gap to quarter panel, there's nothing you can do to fix it, but start over or get the port-o-power out. Also a tip, do one side at a time so you can check the other side for clues on proper position. Once post is in the right spot, it's just spot welds then paint - not that bad. One last tip - be sure to drill all your spot weld (plug weld) holes with the post off the truck, and prep the surface these weld to by grinding and cleaning real well, then spray with weld-thru primer all sides that will be hidden.
