I don't want to re-invent the wheel

TB
That 15" steel Rally of mine, at 4.5BS, rubbed on the Upper BJ, at near full droop, and the BJ ripped all the wheel weights right off, at ride height. The caliper rubbed in a few places too, which I had to correct. And the tire rubbed on the frame at full lock, and on the strutrod the other way.. In my application, the 4.5bs was right at the limit, if not slightly over,lol..
This was on a 68 Barracuda with the KH 4-piston calipers and the suspension lowered about 1inch. The Demon should be the same situation.
As I recall you have a 73 up Dart which with the slider caliper system, has a slightly wider front track; about .375 as I recall. So the 4.5 may work on yours, or if you already have it then it does,lol. Am I wrong?