Both completely different:
70 Cuda 5 Bow
70 Challenger 5 Bow
71 Cuda 4 and / or 5
71 Challenger 4 and / or 5
70-71 Grand Coupe Cudas masonite / cardboard w/ mtl. on top
70-71 RT/SE Challenger masonite / carboard w/ mtl. on top
72 Challenger 4 bow perforated material
72 Cuda 4 bow perforated mtl
73 -74 Yorkshire material (non perforated)
Cuda use a sail board behind rear 1/4 windows, Challengers do not.
Sunroof cars obvious.
I'm sure there were some 73's with perforated mtl and vice versa on late 72's using Yorkshire mtl.
Probably more differances too but that's all I have to offer.