The original Mopar suspension design is very good. So good, that 50 years later it still works just fine at 150 mph on any road race course. Wheel travel is one limitation as is ride height. You just can't get the factory suspension low enough to go really fast. If you lower the car too much you run out of travel and then you hit the wall when the suspension bottoms out. Some mods can be made, but they start to get rather involved.

One really big drawback is the factory steering box and linkage. And to change that over to a rack requires a bucket load of changes. Which then naturally leads to products like what MagnumForce and RMS and others are building.

But, if you're willing to live with the limitations of the factory ride height and steering box, and you can build headers that clear the torsion bars, then the factory suspension design works just fine up past 150 mph road racing.

For a 200 mph car you would need to make some fairly significant changes.