You probably don't want to hear this, but there are no repro handles for the Chally...
You are correct in that the Challenger handles are concave and the Cuda ones are convex.
I have seen some replacement handles that are actually flat... they probably figured that it was a good enough fit for both cars. Most of the after market repop'd ones I've seen are for Cuda... They are convex. The catalogs will say they are for e-bodies because they are... They do fit both cars, after all...
I have yet to see any replacement/repros that are concave like the Challenger is supposed to be.
If you want them to fit perfectly, you're gonna have to get yours refinished.