Restoring opened wheel arches

[Jantrix]

I have an old build (51 Fleetline custom) that I was planning on doing as a modern custom. However changes I have made to the car give it a decidedly traditional kustom feel to the car. However I had already opened the wheel arches for the 20 inch wheels. I'd like to close them back in and reshape them a bit. What is the best way to restore the size/shape of the openings, without cutting up a second body? Thanks in advance.