1972 Canadian H-Code 340 Dart Swinger Special Resto - Finally started!
I had exactly the same problem with my quarter panels and after I gave up on moving them any further forward there was only two options left, alter the quarter panel or alter the edge of the trunk lid.
It would have been a many hours of work and messed up a lot of the inside that I had done and warped the top of the quarters so I chose to grind the edge of my trunk lid back to the gap I wanted and cooling the weld with air as I went welded up the edge and finish it with a mini grinder and sander, you can see by how little damage this did to the primer that it had no effect on the trunk lid skin as far as warping and it took an hour or two compared to many hours and filler and nobody would know it was a problem. Just remember that you have to remove enough knowing the weld itself will build it back out some.
Hope that helps you out
Red383.