Got a bit more done on the filet-O-fish today. Got the outer wheelhouse aft end fitted and welded, pulled in the front end of the trunk drop to line up better, hammer and dolley worked the rear half of the rear quarter skin to fit at the valance much better.
I also welded back in the wiring harness retaining clips. I wrote the dimensions where they were attached on the old trunk drop with a sharpie. Took a pic of it, and put them back in the exact same spots on the new drop.
Using a dolley and various body hammers, I was able to roll the lip on the valance, and on the rear of the quarter skin to get it to tuck behind the valance like the factory ones does.
It was an awful lot of work making this stuff play nice with one another, but it plays nice now, and the quarter skin just falls right into place in these areas. It's looking like I have to mod the outer wheel house arch next, and the quarter skin at the front to fit better, but that's an installment for a later date.
Overall I am pretty happy with the progress so far.