54 Chevy Truck.... left to die

[FarmerSid]

Ok. See it now. Are you going to leave it and add filler to even it out? If it were me and seeing that I recently had to do it, I would cut the panel in the area that is sunk it in the door opening area and pull it out. You have to do this with the door on to make sure you get things nice and flush. It's also easy to get in behind and use a copper backer when welding.