Between quarters I would go out a fiddle a little with the cab corner.
Welded the seem with stitch welds.
I only had to go back and redo two really small holes after grinding. Did that and grounded it down:
Overloaded it with body filler:
Sanded down the filler:
A little more filler will be required right in the silver area in the photo as when you run your hand over it you can feel a bit of a dip.