Demon front end conversion. INPUT??

The Valiant front clip won't work for several reasons. The Demon has extensions on the fender, the hood is longer, and the front wheel well openings are different between the Valiant & Dart. Any Dart 70-72 front clip ought to work. The 72 fenders will use the same marker lights you have on the Dart Sport.
The Demon has specific logo panels on the front edge of the doors on the inside. The tail panel & lights are unique as well. I've seen the lights pop up on e-bay from time to time. Never have seen a tail panel for sale. As far as I know, these are not available in repo. Since the Demon was only made in 71 & 72, the potential for supply at this point is going to be small. Good luck.
The Demon logo on the tail is always a decal. On the front fenders it is metal unless it has the stripes like mine, then it is decal, too.