[Wiseguy59]

Leave the quarter panel alone, and make the wheelhouse fit the quarter.
You'll have to split the lower portion of the wheelhouse and open it to fit the quarter.
Then you'll have to fill in the open area of the wheelhouse.
That looks a little worse than mine, but I wound up getting mine to fit.
It just takes time. Go slow and it will all come together.

 

[Wiseguy59]

That's about what you have to do.
Just cobble something together that closes the gaps as best as possible, and looks decent, which is why I used the lower portion of the patch panel.
It was kind of a wast using such a small part of it, but it went in nicely.
It's a tough area to get to with a grinder, so weld slowly.