Let's look at it this way,

3,200# e-body.
Hotchkis suspension with 1.10" torsion bars & adjustable fox-shocks.
13" Baer / Wilwood / Dr.Diff brakes.
Modern, custom or (modern Ford) 17-18" wheels with -good- tires.
Ready-to-run on a crate, 5.7 Hemi & TR6060 trans for 6-8k (eBay).
Hydroboost swap.
Power steering, 14:1 ratio.
-way- ahead of trying to Frankenstein an lx mopar / gm chassis and challenger body. I don't even see why a custom chassis even comes into the equation, when all the testing / R&D has been done with the factory style suspension upgrades from companies like Hotchkis.

You do know the new Ford GT runs a torsion bar suspension right? It won the 24-hour of Le Mans. Unfortunately, we don't have a valve actuated coil spring to manipulate our ride height / spring rate.

There is no reason why a Challenger can't be built to handle / perform exceptionally well, without going into the deep end financially and using off-the-shelf parts. It will just take more effort to drive at the limit, but the limit is exactly the same. Ever turned all the electronic management systems off on a modern car making 400+ HP? Don't.