I've seen a number of 1st gen Falcon's with a similar radius. Most bought junk front fenders and cut the metal out of those to make the rear radius. I found a late 70's Mercedes nosed at the local Pick N Pull, and bought the radius I cut off the front fenders for $10. It worked great for my rear radius.
I also filled in the trailing edge of my trunk drops as I didn't care for the way they sloped back from the slicks.